Apollo.io API: Complete Developer Guide for B2B Sales Teams

What is the Apollo.io API?

Apollo.io offers a REST API that enables sales teams and developers to programmatically access their B2B database of contacts and companies. The API allows you to search for leads, enrich existing contact data, manage sequences, and sync information with your CRM or other sales tools.

Unlike using Apollo's web interface, the API lets you automate prospecting workflows, build custom integrations, and process contact data at scale. Whether you're enriching leads in your CRM, building a custom prospecting tool, or automating your outreach pipeline, the Apollo.io API provides endpoints for most actions available in the UI-plus some additional functionality exclusive to API users.

The Apollo API is a standard REST API that uses JSON for requests and responses, making it language-agnostic. You can interact with it using any modern programming language that can make HTTP requests, such as Python, JavaScript, Ruby, Java, or PHP. This flexibility makes it accessible to developers regardless of their preferred tech stack.

Getting Started with Apollo API Authentication

Before making your first API call, you'll need to generate an API key from within the Apollo platform. Navigate to Settings > Integrations, find the API option, and click Connect to create and view your key. This key is your unique identifier that tells Apollo's system you have permission to access and request data.

Apollo offers two types of API keys: standard keys with limited endpoint access and master keys that provide access to all endpoints including administrative functions. Some endpoints, like Get a List of Users, are only accessible with a master key. When creating your key, you can select specific API endpoints for access or toggle "Set as master key" to select all endpoints.

The API key should be included in the header of your API request using the x-api-key header field. Apollo's API is accessible only under HTTPS with valid certificates for all API methods, ensuring secure data transmission for all calls.

For developers building integrations intended for multiple Apollo users, you'll need to implement OAuth 2.0 authorization when building your integration. This allows you to query endpoints on behalf of mutual users while maintaining proper security protocols.

Apollo.io API Pricing: What You'll Actually Pay

Here's where Apollo's pricing gets complicated. While the base subscription prices look straightforward, the API operates on a consumption-based model with multiple credit types.

Plan-Based API Access

All Apollo customers get basic API access, but the level of access depends on your plan:

• Free Plan: Limited API access with 100 credits per month, daily rate limit of 600 requests
• Basic Plan ($49/user/month billed annually): 5,000 email credits, daily rate limit of 2,000 requests
• Professional Plan ($79/user/month billed annually): More credits and higher rate limits
• Organization Plan ($119/user/month billed annually): Advanced API access, 15,000 monthly credits, and the highest rate limits

Annual billing provides a substantial discount-up to 20% compared to monthly billing. If you choose monthly billing, the Basic plan costs $59/user/month, Professional costs $99/user/month, and Organization costs $149/user/month.

The Credit System Explained

Apollo's API consumes credits for various actions:

• Email addresses: 1 credit per business email found
• Mobile numbers: 8 credits per phone number revealed
• Export credits: 1 credit when you export or sync data to external systems like your CRM

This is where costs can spiral. If you run out of credits, additional credits cost approximately $0.20 each with a minimum purchase of 250 credits monthly or 2,500 annually. Critically, unused credits expire at the end of your billing cycle-no refunds or extensions.

The credit allocation varies across plans significantly. Free users get 100 credits, Basic users receive 5,000, Professional users get 10,000, and Organization level subscribers receive 15,000. However, there's an important caveat: free plan users with a valid and verified corporate domain actually get 10,000 credits per account per month, while customers without a valid corporate domain have an even lower credit limit of just 100 credits per account per month.

Understanding Email Credit Limits

While Apollo markets "unlimited" email discovery credits on paid plans, there are actually caps in place. The platform has implemented an email credit limit for paying customers of the lesser of two options: the dollar amount paid by the customer for the term of their subscription divided by $0.025, or 1 million email credits per account per year unless a different credit limit is specified in the Order Form.

For non-paying accounts on an Unlimited Plan, the credit limit is 10,000 credits per account per month. For paying accounts on an Unlimited Plan, it's the lesser of $ Paid / $0.025 or 1 million credits per account per year. This means your actual credit availability depends on both your plan tier and your total spend.

Apollo.io API Rate Limits

Apollo uses a fixed-window rate limiting strategy with limits that vary by endpoint and plan. Here's what you need to know:

• API tokens are typically limited to 100 requests per 5 minutes on lower tiers
• Each endpoint has separate rate limits per minute, hour, and day
• The free plan allows only 600 API requests daily
• Basic and Professional plans allow 2,000 daily requests
• Default enrichment rate limits are 1,000 per hour
• Paid plans increase the rate limit to 200 requests per minute

When you exceed limits, calls return HTTP status 429. You can monitor your usage through response headers or the API usage stats endpoint (requires a master API key). If you need higher limits, you'll need to contact Apollo sales for a custom plan.

As an example of this fixed-window strategy, if your team's rate limit is 200 requests per minute, those requests can be made at any interval within a 60-second window. Once that window closes, your limit resets. Your Apollo pricing plan directly impacts the rate limits for API endpoints, so upgrading your plan is often necessary as your usage scales.

Apollo shows the rate limits for each of the API endpoints in your developer dashboard, revealing how many calls you can make per day, hour, and minute. You can also reference the headers of a successful response from the API to view how many requests your current plan allows and how many requests you have used. The rate limits are enforced on a per-token basis, so multiple API keys can help distribute load across different integrations.

Key Apollo.io API Endpoints

The Apollo API offers several categories of endpoints for B2B sales operations:

People and Organization Data

• People Enrichment: Enrich contact records with email, phone, title, and company data
• Bulk People Enrichment: Process multiple contacts in a single request (note: rate limits are 1/10th of single enrichment)
• Organization Enrichment: Get company data including size, industry, tech stack, and funding
• People Search: Find contacts using filters like title, company, location, and industry
• Organization Search: Search for companies matching specific criteria

CRM and Automation

• Accounts: Create, update, and bulk create company records
• Contacts: Manage individual contact records
• Sequences: Modify outreach sequences programmatically
• Tasks: Update task priority, due dates, and custom fields
• Deals: Create, list, and view deal information
• Calls: Create call records, search for calls, and update call records
• Users: Get a list of users in your organization

Important Implementation Notes

By default, most endpoints don't return email addresses or phone numbers. You need to explicitly request this data using parameters like reveal_personal_emails and reveal_phone_number on the people enrichment endpoint. Each reveal consumes credits from your allocation.

Apollo relies on the information you pass via the endpoint's parameters to identify the correct person to enrich. If you provide more information about a person, Apollo is more likely to find a match within its database. If you only provide general information, such as a name without a domain or email address, you might receive a 200 response, but the response will indicate that no records have been enriched.

The People API Search endpoint is optimized for API usage and does not consume credits, making it an excellent starting point for identifying prospects before spending enrichment credits. Use this endpoint with tight filters to identify prospects that match your ICP criteria before enriching their contact data.

Testing and Developing with Apollo's API

Apollo provides a robust testing environment directly in their developer documentation. You can test all of Apollo's public API endpoints directly on their documentation site without writing any code. Simply enter your API key in the Header field, choose one of the available programming languages, and enter details in the parameters to generate your API request.

At a minimum, you need to address the required parameters. As you add values to the parameters, the API request updates live, showing you exactly what will be sent to Apollo's servers. Click "Try It!" to send your request and view the response, including the complete schema.

If you're not ready to test, you can review example responses (including schema) for every endpoint without testing. This makes it easy to understand what data you'll receive before committing development resources. Keep in mind that your access to endpoints is potentially limited by your team's Apollo.io pricing plan and the scopes you apply to your API key.

Common Apollo.io API Use Cases

Sales and marketing teams typically use the Apollo API for:

• CRM Enrichment: Automatically populate contact and company fields in Salesforce, HubSpot, or other CRMs
• Lead Scoring: Pull in firmographic data to score and prioritize leads
• List Building: Programmatically search for contacts matching your ICP criteria
• Data Hygiene: Verify and update existing contact records regularly
• Custom Workflows: Build prospecting tools tailored to your specific sales process
• Real-Time Enrichment: Enrich new leads instantly as they enter your system from web forms or other sources
• Trigger-Based Automation: Automatically enrich accounts when they show buying intent signals
• Lead Routing: Automatically assign enriched leads to the appropriate sales rep based on territory, industry, or company size

One particularly powerful use case is real-time enrichment combined with trigger-based outreach. When someone registers for your webinar or visits your pricing page, an enrichment tool can instantly append their company info and push them to your sales engagement platform, which triggers a rep to call within minutes. This kind of agile, real-time approach can dramatically increase connect rates and conversion.

For teams working across email, social media, and CRM platforms, Apollo's API enables multichannel strategies by ensuring that enriched data flows seamlessly between systems. You can build workflows that waterfall between multiple data providers, using Apollo as your primary source and falling back to alternatives when Apollo doesn't have the data you need.

Building Custom Integrations with Apollo's API

Apollo's API enables sophisticated custom integrations that go far beyond simple data enrichment. Developers can build entire sales intelligence platforms that leverage Apollo's 210M+ contact database alongside proprietary data sources and custom logic.

Webhook Support and Real-Time Updates

While Apollo doesn't offer native webhook functionality in the traditional sense, you can implement webhook-like functionality using external services or custom server-side code. Many teams use platforms like Zapier, Make (formerly Integromat), or Pipedream to create webhook integrations between Apollo and other tools in their stack.

For example, you can set up workflows that trigger when new accounts or contacts are created or updated in Apollo, automatically pushing that data to other systems or triggering custom actions. This enables event-driven architectures where changes in Apollo cascade through your entire sales tech stack.

Batch vs. Real-Time Processing

Apollo supports both batch processing and real-time enrichment, each with distinct advantages. Batch processing is ideal for enriching historical data-you can upload a CSV of 10,000 contacts and enrich them all at once, cleaning up your existing database. The bulk people enrichment endpoint lets you process up to 10 people with a single API call, reducing your request count against rate limits.

Real-time processing, on the other hand, enriches data the moment it enters your system. When a new lead fills out a form with just their email and company, an integrated enrichment service can instantly populate the rest (name, title, company details) before your rep even picks up the phone. This ensures your team always has the latest information when engaging prospects.

Many companies adopt a hybrid strategy: run a massive batch process to clean up historical data, then switch on a real-time API to keep every new lead fresh and actionable from day one. This gives you the best of both worlds, ensuring both old and new data is always reliable and ready to use.

Integration with CRM Platforms

Apollo offers native integrations with major CRMs like Salesforce, HubSpot, and Zoho CRM at no extra charge on paid plans. However, each contact sync to these platforms uses up an export credit. This becomes a substantial expense for teams that heavily rely on CRM synchronization.

For deeper integrations, you can use Apollo's API to build custom sync logic. This allows you to control exactly when and how data flows between Apollo and your CRM, potentially reducing credit consumption by only syncing qualified leads or enriching specific fields rather than entire records.

When integrating with other APIs like Freshsales, Pipedrive, or Capterra, always refer to their respective documentation for specific integration guidelines. Each CRM has its own unique data structures and authentication methods, so it's crucial to understand these differences to ensure smooth integration. Consider using middleware or integration platforms to simplify the process and maintain reliable data flow.

The Hidden Costs of Apollo's API

Before committing to Apollo's API, consider these often-overlooked expenses:

• Export Credit Burn: Every API call that syncs data externally consumes export credits-this adds up fast when integrating with multiple tools
• Credit Expiration: Unlike some platforms, unused credits don't roll over. You either use them or lose them
• Feature Gating: Advanced filters like technographics, hiring data, funding rounds, and intent signals require higher-tier plans
• Data Quality Issues: Some users report being charged credits even when data is wrong or unavailable
• Integration Costs: Premium integrations with Salesforce and Outreach are locked behind higher tiers
• Mobile Number Premium: At 8 credits per phone number, costs escalate quickly if your outreach relies on calling
• Minimum Purchase Requirements: You can only buy 250 monthly credits upwards or 2,500 annual credits upwards at a time
• Seat Flexibility: You cannot reduce the number of seats until your payment term ends, limiting downscaling options

These limitations often push teams to supplement Apollo with additional tools. For verifying the contacts you pull from Apollo, consider using a dedicated email verification tool to avoid wasting outreach on invalid addresses.

The hybrid pricing model-fixed seat fee plus usage-based credits-sounds flexible, but in practice, it often leads to budget volatility. Credits are consumed every time your team reveals a contact, accesses a mobile number, or exports data. That may seem manageable at first, but once your team begins using the platform actively, those credits disappear fast. Suddenly, your "affordable" tool starts costing hundreds more per user.

Data Quality and Accuracy Considerations

While Apollo boasts a massive database of 210M+ contacts, data quality remains a common concern among users. Phone numbers aren't reliable enough for heavy cold calling, and some reviewers report inaccuracies in contact information, particularly for international markets outside the United States.

Data accuracy issues can be particularly problematic because you're charged credits even when the data returned is incorrect or outdated. Unlike some providers that offer credit-back guarantees for bad data, Apollo's credit consumption happens regardless of data quality.

For this reason, it's critical to implement a verification layer before using Apollo data for outreach. Run email addresses through a dedicated email verification service before launching campaigns. This protects your sender reputation and avoids wasting sequence touches on invalid contacts.

B2B data goes stale fast-at a rate of 25-30% per year. People change jobs, companies get acquired, and contact information becomes outdated. To maintain data quality, establish automated refresh cycles that re-enrich records periodically. Most experts recommend refreshing enriched data every 3-6 months to maintain accuracy, though rapidly changing information like contact details may require monthly updates.

Alternatives to the Apollo.io API

If Apollo's credit system feels restrictive or unpredictable for your needs, several alternatives offer different pricing models:

For B2B Targeting and ICP Development

Before you invest in an API for lead enrichment, make sure you've clearly defined your target market. Our B2B Targeting Generator uses AI to analyze your ideal customer profile and generate detailed targeting criteria-free, with no credit system to worry about. This ensures you're enriching the right contacts from the start, avoiding wasted credits on prospects outside your ICP.

For Email Verification

Apollo's email data accuracy varies, and you're charged credits regardless of whether the email is valid. Before launching outreach campaigns, run your contact list through Galadon's Email Verifier to instantly check if an email is valid, risky, or invalid. This protects your sender reputation and improves campaign deliverability without consuming additional API credits.

For Contact Discovery

If you need to find email addresses from names and companies, Galadon's Email Finder offers a straightforward alternative without the complexity of Apollo's credit system. You can also use our Mobile Number Finder to locate cell phone numbers from email addresses or LinkedIn profiles-particularly useful since Apollo charges 8 credits per phone number.

For Multichannel Outreach

Platforms like Lemlist and Reply.io offer email and LinkedIn automation with more transparent pricing. They're particularly strong for teams focused on personalized outreach rather than pure data extraction. Both platforms provide their own contact enrichment features without the confusing multi-tiered credit systems.

For Contact Enrichment

If you primarily need contact data, RocketReach and Lusha offer API access with different credit structures that may suit your volume better. Both platforms offer unrestricted pricing models that don't penalize you for exporting data to your CRM, making total cost more predictable.

For Sales Automation at Scale

Tools like Clay combine data from multiple sources with automation capabilities, letting you waterfall between providers to maximize coverage while minimizing cost per lead. Clay's approach allows you to try Apollo first, then fall back to other providers if Apollo doesn't have the data, ensuring you only pay for successful enrichments.

For Technology Intelligence

If you need to identify companies using specific technologies, Galadon's Tech Stack Scraper provides this functionality without requiring a full Apollo subscription. This is particularly useful for targeting companies based on their technology infrastructure-a capability Apollo locks behind higher-tier plans.

Practical Tips for Using Apollo's API Efficiently

If you decide Apollo's API fits your needs, here's how to maximize value:

1. Batch Your Requests

Use bulk endpoints where available. The bulk people enrichment endpoint lets you process multiple contacts in one call, reducing your request count against rate limits. However, keep in mind that bulk enrichment rate limits are typically 1/10th of single enrichment limits, so plan accordingly.

2. Cache Aggressively

Store Apollo data locally to avoid re-requesting the same information. Credits are charged per request, not per unique record. Implement a caching layer that stores enriched data for a reasonable period (30-90 days) before refreshing. This dramatically reduces credit consumption for frequently accessed records.

3. Filter Before Enriching

Use search endpoints with tight filters to identify prospects before spending enrichment credits. Don't enrich contacts that don't match your ICP. The People API Search endpoint doesn't consume credits, making it perfect for building targeted lists before enrichment. Define criteria like job title, seniority, company size, industry, and location to narrow your list to only high-quality prospects.

4. Monitor Your Usage

Set up tracking through the API usage stats endpoint. Apollo's developer dashboard allows real-time monitoring of credit consumption-use it to avoid surprise overages. Your current rate limit usage is returned in the response headers from each request you make, so instrument your code to track this automatically and alert you when approaching limits.

5. Verify Separately

Rather than trusting Apollo's email data blindly, run addresses through a dedicated email verification service before outreach. This protects your sender reputation and avoids wasting sequence touches on invalid contacts. The cost of verification is typically far less than the reputational damage from high bounce rates.

6. Use the Right Enrichment Method

Choose between batch processing and real-time enrichment based on your use case. Batch processing is ideal for cleaning up existing databases, while real-time enrichment ensures new leads are actionable immediately. Don't enrich records in real-time that could be processed in scheduled batches-you'll save on rate limit consumption.

7. Optimize Your API Call Structure

Minimize the amount of data you request in each call. Only request the fields you actually need rather than pulling complete profiles. Use pagination effectively when retrieving large datasets, and implement proper error handling to manage rate limit errors gracefully with exponential backoff retry mechanisms.

8. Leverage Automation and Integration

Connect your enrichment tool directly to your CRM so enriched data flows in automatically without manual work. Set up automation rules that trigger enrichment based on specific events-like when a lead reaches a certain score threshold or when a contact hasn't been updated in 90 days. This eliminates manual steps and ensures your team always has fresh data.

Security and Compliance Considerations

When implementing Apollo's API, security and compliance should be top priorities. Apollo's API uses API keys for authentication, which should be treated as sensitive credentials. Never hardcode your API key directly into your code. Instead, use environment variables or secure configuration management systems to store keys.

For data privacy, ensure your enrichment practices comply with GDPR, CCPA, and other relevant data protection regulations. Enriching data often involves collecting and processing additional personal information, which can raise privacy concerns. You need consent to use the data for enrichment purposes, and you should implement proper data retention policies that align with regulatory requirements.

Apollo offers SSO (Single Sign-On) and advanced security configurations on the Organization plan, which is essential for large organizations with strict security requirements. If you're building an integration for multiple users, implement OAuth 2.0 properly and follow Apollo's partnership requirements for marketplace listing.

Performance Optimization and Scalability

As your usage grows, performance optimization becomes critical. Here are strategies to ensure your Apollo API integration scales effectively:

Implement Queueing Systems: For high-volume enrichment, implement a queue-based system that processes enrichment requests asynchronously. This prevents rate limit issues and allows for better error handling and retry logic.

Use Async Processing: Leverage asynchronous API calls for large-scale projects. Apollo's API supports both synchronous batch scraping and asynchronous approaches, with async being particularly useful for enriching datasets containing 10,000+ records.

Distribute Load: Create multiple API keys for different integrations or teams. Since rate limits are enforced on a per-token basis, this allows you to distribute load across different keys and avoid bottlenecks.

Monitor and Alert: Set up monitoring for API usage, error rates, and response times. Create alerts when you approach rate limits or when error rates spike, allowing you to respond proactively before issues impact your team.

Plan for Off-Peak Processing: Schedule batch enrichment jobs during off-peak hours to reduce the chance of hitting rate limits. This is particularly important for large-scale data refresh operations.

Should You Use Apollo's API?

The Apollo.io API is a solid choice if:

• You're already using Apollo's platform and want to automate workflows
• Your prospecting volume is predictable month-to-month
• You're on a paid plan that includes sufficient credits for your needs
• You need a single platform for both data and outreach automation
• Your target market is primarily US-based companies
• You have development resources to build proper caching and error handling
• You can commit to annual billing to get the 20% discount

Consider alternatives if:

• Your data needs fluctuate significantly
• You want predictable, unlimited-style pricing
• You primarily need mobile numbers (at 8 credits each, costs escalate quickly)
• You're building a product that resells B2B data
• You target international markets where Apollo's coverage is weaker
• You need strong data accuracy guarantees
• You want the ability to scale down seats mid-contract
• You're a small team with limited budget for credit overages

Best Practices for B2B Data Enrichment

Regardless of which API you choose, following enrichment best practices ensures maximum ROI:

Establish Clear Data Governance: Define policies for what data gets enriched, how often, and by whom. Create documented standards for data quality and establish ownership of data enrichment processes within your organization.

Implement Data Quality Checks: Audit enriched data for relevance and accuracy on a regular basis. Maintain feedback loops with your API providers so data quality continues to evolve over time. Track key metrics like match rate, accuracy, and data freshness.

Measure ROI: Compare pre- vs. post-API deployment performance to quantify ROI. Track metrics like lead response time, conversion rates, and sales cycle length to demonstrate the value of enrichment to stakeholders.

Automate Refresh Cycles: B2B data decays rapidly-set up automated workflows to refresh enriched data every 3-6 months. For high-value accounts, consider more frequent updates to ensure your team always has current information.

Respect Privacy: Choose platforms that follow GDPR, CCPA, and other data laws. Look for tools that offer consent-based enrichment solutions, consent tracking, opt-out options, and secure data storage. It's your responsibility to ensure compliance with applicable regulations.

Building Your B2B Prospecting Stack

The Apollo API is one piece of a larger sales technology puzzle. Before investing in any data enrichment tool, start with clear targeting. Our B2B Targeting Generator helps you define exactly which companies and decision-makers to pursue-then you can evaluate whether Apollo, an alternative, or a combination of tools best fits your prospecting workflow.

Once you've found your leads, you'll need to verify contact data before outreach. Pair your prospecting with a reliable mobile number finder and email verification to ensure you're reaching real people at real companies. For background research on key decision-makers, consider using a background checker to build comprehensive profiles that inform your outreach strategy.

The best sales teams don't rely on a single tool-they build integrated stacks that maximize coverage while minimizing cost per qualified lead. Whether Apollo's API earns a place in your stack depends on your specific volume, budget, and workflow requirements.

The Future of B2B Data Enrichment APIs

The B2B data enrichment market is experiencing explosive growth, projected to jump from roughly $5 billion to $15 billion over the next several years. This growth is driven by several emerging trends that are reshaping how companies approach data enrichment:

AI-Powered Enrichment: Advanced enrichment platforms increasingly leverage artificial intelligence to improve data accuracy and completeness. AI can match partial information across multiple sources, predict missing data points, and continuously learn from feedback to improve match rates.

Intent Data Integration: Integration with intent data platforms enables even more superior sales intelligence features, allowing firms to discover and pursue prospects at their most opportune point in the purchase cycle. When combined with enrichment data, intent signals help prioritize which enriched leads to contact first.

Real-Time Everything: The shift toward real-time enrichment continues to accelerate. Speed to lead has never been more important-companies that respond to leads within an hour are seven times more likely to have meaningful conversations with decision-makers than those who wait longer.

Waterfall Enrichment: Rather than relying on a single provider, sophisticated teams use waterfall strategies that try multiple sources sequentially, only moving to the next (typically more expensive) source when the previous one fails. This maximizes data coverage while minimizing cost.

Privacy-First Approaches: As regulations tighten globally, enrichment providers are adapting with consent-based models, better transparency around data sourcing, and enhanced compliance features built directly into their APIs.

Conclusion: Making the Right Choice for Your Team

Apollo.io's API offers powerful capabilities for automating B2B prospecting and enrichment, but it's not the right choice for every team. The consumption-based pricing model creates unpredictability, credit expiration policies penalize inconsistent usage, and export credits add hidden costs to CRM integrations.

For teams already embedded in the Apollo ecosystem with predictable, high-volume needs, the API provides valuable automation capabilities. The ability to programmatically access 210M+ contacts, enrich records at scale, and build custom integrations justifies the complexity for many organizations.

However, if you're just getting started with B2B prospecting or need more cost predictability, consider starting with simpler, more transparent alternatives. Galadon's free tools provide many core capabilities-email verification, email discovery, mobile number finding, and ICP targeting-without complex credit systems or API rate limits.

For sales professionals who need not just tools but also expertise, Galadon Gold ($497/month) offers something unique: 4 live group calls per week with sales experts, direct access to proven cold email frameworks, a community of 100+ active sales professionals, and priority support. It's the kind of hands-on guidance that helps you use tools like Apollo (or its alternatives) more effectively.

Ultimately, the best prospecting stack combines reliable data sources, verification layers, and practical expertise. Whether you choose Apollo's API or build a custom stack with specialized tools, focus on data quality, workflow efficiency, and measurable ROI. The tools matter less than how you use them-and having expert guidance to optimize your approach often delivers far more value than any single API.