You need identity resolution. You’ve realized that anonymous traffic, fragmented customer records, and siloed data sources are costing you pipeline. So you start looking for an API that can match unknown signals to known people.
And then you find out there are 10+ options ranging from free open-source IDs to $200K/yr enterprise platforms. Most comparison content is written by vendors who conveniently rank themselves first. This one compares everyone honestly - including Leadpipe, the product we build.
We’re biased, obviously. But we’ll show our work. Every claim here is verifiable, and we’ll tell you when a competitor does something better than us. Fair deal?
What Is an Identity Resolution API
Identity resolution is the process of matching fragmented data points - an IP address here, a browser fingerprint there, an email hash somewhere else - to a single, real person. An identity resolution API exposes this capability as a programmable service. You send in a signal. You get back a person.
This is fundamentally different from contact enrichment. Enrichment starts with a known identity (an email address, a LinkedIn URL) and adds more data to it. Identity resolution starts with an unknown signal and resolves it to a known identity. Think of enrichment as “tell me more about Jane.” Identity resolution is “who is this anonymous visitor in the first place?”
The technical backbone is an identity graph - a data structure that maps relationships between identifiers. Email addresses, phone numbers, device IDs, cookies, IP addresses, and hashed emails all get linked to person records. When a new signal arrives, the API traverses the graph to find the best match. The quality of that graph - its size, freshness, and matching methodology - determines everything about the API’s usefulness.
There are two matching methodologies that matter: deterministic and probabilistic. Deterministic matching requires exact, verified identifier overlap (same email hash, same phone number). Probabilistic matching uses statistical models to infer likely matches based on behavioral signals. Deterministic is more accurate. Probabilistic covers more ground. The best providers are transparent about which method they use and when.
The Big Comparison Table
Here’s how 10 identity resolution APIs compare across the dimensions that actually matter for developers:
| Provider | Pricing | API Access | Match Rate | Matching Method | Person Data | Intent Data | Self-Serve | Data Scale |
|---|---|---|---|---|---|---|---|---|
| Leadpipe (market leader) | $147-$8K/mo | 23 endpoints, SDK, MCP | 30-40% of visitors | Deterministic | Yes (100+ data points) | Yes (20K topics) | Yes | 4.44B profiles |
| FullContact | $99/mo (advertised) | REST API | 40-60% real-world | Deterministic | Yes | No | No (sales required) | 1B+ profiles |
| LiveRamp | $50K+/yr | AbiliTec API | Not published | Deterministic-first | Limited | No | No | Largest auth. graph |
| Experian/Tapad | $50K+/yr | Enterprise API | High | Deterministic + Probabilistic | Yes (bureau-grade) | No | No | Bureau-scale |
| TransUnion/Neustar | $50K+/yr | TruAudience API | High | Deterministic + Probabilistic | Yes (bureau-grade) | No | No | Credit bureau scale |
| 5x5 Data | Membership | Co-op API | Varies | Probabilistic waterfall | Yes | Limited | No | 250M+ contacts |
| Amperity | $200K+/yr | Platform API | High (first-party) | 45 algorithms | Yes | No | No | Customer data only |
| Informatica | $200K+/yr | MDM API | N/A | Rule-based | Yes | No | No | Enterprise records |
| mParticle | CDP pricing | IDSync (4 endpoints) | Varies | Cross-device | Limited | No | No | CDP-scoped |
| Lotame | Partnership-based | Panorama ID API | Moderate | Probabilistic | No (segments) | No | No (partnership required) | Publisher data |
Match Rate Comparison by Provider
Bar widths represent approximate published or estimated match rates. Gray bars indicate unpublished rates. Purple bars indicate probabilistic matching.
Key insight: “Match rate” means different things across these tools. Leadpipe measures the percentage of anonymous website visitors it can resolve to real people. FullContact measures enrichment hit rates against submitted identifiers. Enterprise providers often don’t publish rates at all. Compare carefully.
Deep Dive: All 10 Providers
1. Leadpipe
What it is: A self-serve identity resolution API built for B2B teams and platform developers. Leadpipe maintains its own identity graph with 4.44 billion person profiles and resolves anonymous website visitors to full contact records using deterministic matching.
API architecture: 23 REST endpoints split across two products. The Data API (5 endpoints) handles visitor identification - pixel management, visitor queries, and account operations. The Intent/Orbit API (18 endpoints) handles topic discovery, audience building, export, and analytics across 20,735 intent topics. Auth is via X-API-Key header with sk_ prefixed keys. Rate limit: 200 requests/minute authenticated.
What you get back: 100+ data points per resolved person, including name, personal and work email, phone numbers, photo, age, gender, income, net worth, LinkedIn URL, Facebook, other social profiles, job title, seniority, full work history, company name, industry, employee count, revenue range, NAICS/SIC codes, HEMs (hashed emails - SHA256, SHA1, MD5), cookies, device IDs, pages viewed, visit timestamps, and person-level intent signals. That’s not enrichment bolted on - it’s the most comprehensive identity response payload available from any self-serve provider.
Developer experience: The most complete developer ecosystem in identity resolution - TypeScript SDK (npm install @leadpipe/client), MCP server for AI agents (npx -y @leadpipe/mcp), real-time webhooks, flat file/CSV exports, and REST API. The SDK is MIT-licensed and open source. No other provider offers this breadth of delivery options.
What it doesn’t do: Person-level resolution is US-focused (company-level globally). No social profile enrichment beyond LinkedIn. The 30-40% match rate means 60-70% of visitors remain unidentified - though that’s still typically 240-300% more than competitors.
Pricing: $147/mo starter (500 IDs). Scales to ~$8,000/mo for high-volume (1M+ identifications) - cost per resolution drops from $0.29 to ~$0.008 at scale. Self-serve signup, no sales call, no annual contract.
Best for: B2B teams wanting visitor identification + intent data in a single API. Platform builders who need to embed identity resolution into their product.
2. FullContact
What it is: An API-first identity resolution platform focused on enrichment and cross-device recognition. FullContact maintains its own identity graph with 1B+ person profiles and specializes in matching known identifiers (emails, phone numbers, social handles) to enriched person records.
API architecture: REST API with endpoints for person enrichment, company enrichment, and identity resolution. Clean documentation, predictable response schemas. The API is genuinely well-designed for developers.
What you get back: 900+ enrichment attributes per person including social profiles, demographics, location, and interests. Strong social media data (Twitter, LinkedIn, Facebook profiles). Good at matching emails to fuller profiles.
What it doesn’t do: No visitor identification - you can’t identify anonymous website visitors. No intent data. No webhook streaming for real-time delivery. Single-source deterministic matching means if the identifier isn’t in their graph, you get nothing.
Match rate reality: FullContact markets 85%+ match rates, but independent tests show 40-60% in real-world scenarios depending on your input quality. Email-based lookups perform best. Phone and name-based lookups are less reliable.
Pricing: FullContact advertises pricing from $99/mo, but access requires a sales conversation. Despite listing prices on their site, you’ll need to contact their team to get started.
Best for: Teams that already have contact records and want to enrich them with social and demographic data. Not for discovering unknown visitors.
3. LiveRamp
What it is: The industry’s largest authenticated identity graph, exposed through the AbiliTec API. LiveRamp connects offline and online identifiers at massive scale and is the default infrastructure layer for many large enterprises and ad-tech platforms.
API architecture: AbiliTec Link and AbiliTec Maintenance APIs. Well-documented but access requires an enterprise agreement. No self-serve option. Integration typically involves working with a LiveRamp solutions architect.
What you get back: AbiliTec IDs - persistent, privacy-safe identifiers that link disparate records. LiveRamp doesn’t return raw PII through the API. Instead, you get linkage keys that let you connect your own first-party data across systems. This is identity resolution as infrastructure, not as a contact database.
What it doesn’t do: No person-level contact data returned through the API (by design). No intent data. No visitor identification. This is a plumbing layer, not a marketing tool.
Pricing: $50K+/yr. Enterprise agreements only. Pricing scales with data volume and use cases.
Best for: Enterprise teams with large first-party datasets that need to connect records across systems. Ad-tech platforms building on authenticated identity. Not for SMB or mid-market.
4. Experian/Tapad
What it is: Bureau-grade identity resolution combined with Tapad’s cross-device graph. Experian brings credit bureau data depth (the most verified consumer data in the US). Tapad adds cross-device matching that connects phones, tablets, laptops, and connected TVs to the same person.
API architecture: Enterprise APIs with strict access controls. Data use agreements required. Integration is a multi-week project involving legal, compliance, and technical teams.
What you get back: Highly accurate consumer identity data backed by credit bureau records. Cross-device graphs for connecting multi-device journeys. Bureau-grade verification that other providers can’t match.
What it doesn’t do: Not self-serve. Not designed for B2B use cases (consumer-focused). No intent data. No real-time visitor identification. Integration timelines measured in months, not minutes.
Pricing: $50K+/yr minimum. Custom enterprise pricing based on data volume, use cases, and regulatory requirements.
Best for: Financial services, insurance, and healthcare companies with compliance requirements that demand bureau-grade verification. Consumer marketing at scale.
5. TransUnion/Neustar
What it is: TruAudience identity resolution backed by TransUnion’s credit bureau data. Similar positioning to Experian but with Neustar’s legacy in telecommunications and digital identity.
API architecture: TruAudience APIs for identity resolution, audience targeting, and measurement. Enterprise-gated with strict data governance requirements.
What you get back: Bureau-grade identity data, particularly strong in consumer financial data. Good cross-device matching through Neustar’s OneID system. Trusted in regulated industries.
What it doesn’t do: Same enterprise limitations as Experian - not self-serve, no B2B focus, no intent data, no real-time visitor identification. The onboarding process involves compliance reviews and data use agreements.
Pricing: $50K+/yr. Enterprise contracts with custom pricing.
Best for: Regulated industries (finance, insurance, telecom) that need credit-bureau-verified identity data. Enterprise marketing teams with budget for premium identity infrastructure.
6. 5x5 Data
What it is: A co-op model identity resolution platform where members contribute data and get access to a shared identity graph. 5x5 uses a probabilistic waterfall approach - trying cookies first, then IP resolution, then hashed email matching.
API architecture: Member API with endpoints for identity resolution and audience building. Access requires co-op membership and data contribution agreements.
What you get back: 250M+ contacts resolved through the co-op graph. The waterfall approach means you get the best available match from multiple methods. Person-level data including email, phone, and mailing address.
What it doesn’t do: Membership required - you can’t just sign up and start querying. The co-op model means your data quality depends partly on what other members contribute. Probabilistic matching means lower accuracy on individual records compared to deterministic approaches.
Pricing: Membership-based. Pricing depends on data contribution and query volume.
Best for: Companies with large first-party datasets willing to participate in a data co-op. Direct-to-consumer brands with significant mailing list data.
7. Amperity
What it is: A customer data platform (CDP) with identity resolution as a core feature. Amperity uses 45 proprietary matching algorithms to unify customer records across systems - CRM, email, POS, web, mobile.
API architecture: Platform API for accessing unified customer profiles. The identity resolution happens inside the platform, not as a standalone API call. You ingest data into Amperity, it resolves identities, and you query or export the results.
What you get back: Unified customer profiles built from your own first-party data. Amperity doesn’t add external data - it deduplicates and connects what you already have. Strong at matching messy records (typos, name variations, address changes).
What it doesn’t do: No external identity graph. No anonymous visitor identification. No intent data. This is a data unification tool, not a discovery tool. You can’t query “who visited my website?” - only “how do my existing records connect?”
Pricing: $200K+/yr. Enterprise platform pricing. Implementation projects typically run $50K-$100K.
Best for: Retail and e-commerce companies with millions of customer records across multiple systems that need deduplication and unification. Not for B2B lead generation.
8. Informatica
What it is: Master Data Management (MDM) with identity resolution capabilities. Informatica’s focus is enterprise data quality - deduplicating, standardizing, and connecting records across large organizations.
API architecture: MDM APIs for record matching, merging, and governance. Part of a much larger data management suite. Integration is an enterprise IT project, not a marketing initiative.
What you get back: Clean, deduplicated master records. Rule-based matching that you configure for your specific data model. Strong data governance and lineage tracking.
What it doesn’t do: Not a marketing tool. No external identity graph. No visitor identification. No intent data. No enrichment. This is about data hygiene for enterprise systems (ERP, CRM, supply chain), not about identifying prospects.
Pricing: $200K+/yr for the MDM suite. Often bundled with other Informatica products.
Best for: Enterprise IT teams managing data quality across large operational systems. Manufacturing, healthcare, and financial services with complex data architectures.
9. mParticle
What it is: A customer data platform with IDSync - a cross-device identity resolution feature built into the CDP. mParticle connects user events across web, mobile, and connected devices using 4 API endpoints.
API architecture: IDSync API with 4 endpoints for identity management. The identity resolution is tightly coupled to the CDP - you can’t use it as a standalone service. Requires mParticle SDK integration on your properties.
What you get back: Cross-device user profiles within your own data ecosystem. mParticle connects the same user across your web app, mobile app, and other touchpoints. It doesn’t add external data - it links your own.
What it doesn’t do: No external identity graph. No anonymous visitor identification beyond your own authenticated users. No intent data. No enrichment. You need the full CDP subscription to access IDSync.
Pricing: CDP subscription required. Pricing based on data volume and monthly tracked users. Typically $50K+/yr for meaningful scale.
Best for: Product teams that need cross-device user tracking within their own app ecosystem. Mobile-first companies with web + app properties.
10. Lotame
What it is: Panorama ID - a free, interoperable identity solution for the ad-tech ecosystem. Lotame’s focus is helping publishers and advertisers maintain addressability as third-party cookies disappear.
API architecture: Panorama ID API for generating and syncing identity tokens. Lotame offers Panorama ID through partnerships, and pricing requires engagement with their team. The business model is built on ad-tech ecosystem participation, not API licensing.
What you get back: Probabilistic identity tokens for connecting users across publisher properties. Audience segments for ad targeting. No person-level PII - this is pseudonymous identity for ad delivery.
What it doesn’t do: No person-level data. No names, emails, phone numbers, or company data. Not designed for B2B use cases. Probabilistic matching means individual accuracy is lower than deterministic approaches. Publisher-focused, not advertiser or sales-team focused. Requires partnership engagement to access.
Pricing: Partnership-based (contact Lotame for access). Not a self-serve signup.
Best for: Publishers and ad-tech platforms that need post-cookie identity for programmatic advertising. Not for B2B sales, marketing, or lead generation.
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Decision Framework: Which API Fits Your Use Case
The right identity resolution API depends on three things: your budget, your use case, and your technical requirements. Here’s how to think about it.
By Use Case
“I want to identify anonymous website visitors and get their contact info.” Leadpipe is the only truly self-serve option - sign up, get an API key, and query data in minutes. No sales call. No partnership agreement. The enterprise options (LiveRamp, Experian) can technically do this, but you’re looking at $50K+ and months of integration. FullContact doesn’t do visitor identification at all. For a full breakdown of the visitor identification approach, see the complete developer guide.
“I want to enrich contacts I already have.” FullContact advertises pricing from $99/mo for social and demographic enrichment, though access requires contacting their sales team. If you need waterfall enrichment across multiple sources, look at Clay or FullEnrich as orchestration layers.
“I need to unify customer records across my own systems.” Amperity for consumer/retail data. Informatica for enterprise IT data. Both are $200K+/yr platform investments, not API subscriptions.
“I need bureau-grade identity verification for regulated industries.” Experian or TransUnion. No alternatives at this tier. Budget accordingly ($50K+/yr).
“I’m building an ad-tech product and need post-cookie identity.” Lotame’s Panorama ID is purpose-built for this, though access requires a partnership engagement. LiveRamp’s authenticated graph is the premium option.
“I’m building an AI agent that needs identity data.” You need an API with SDK support, low latency, and structured responses. Leadpipe’s SDK + MCP server is purpose-built for this. See our guide on identity APIs for AI agents.
By Technical Requirements
| Requirement | Best Options |
|---|---|
| Self-serve API (no sales call) | Leadpipe |
| TypeScript/JavaScript SDK | Leadpipe |
| MCP server for AI agents | Leadpipe |
| Webhook streaming | Leadpipe |
| Batch processing | LiveRamp, Experian, TransUnion |
| Cross-device matching | Experian/Tapad, mParticle, Lotame |
| First-party data unification | Amperity, Informatica |
| GDPR compliance | LiveRamp, Experian, TransUnion |
Pricing Tiers: What You’ll Actually Pay
Self-Serve (Under $1K/mo)
| Provider | Starting Price | What You Get |
|---|---|---|
| FullContact | $99/mo (advertised, sales required) | 1,000 enrichment credits |
| Leadpipe | $147/mo (Starter) | 500 identified visitors + intent data |
| Leadpipe | ~$8,000/mo (High-Volume) | 1M+ identifications, ~$0.008/ID |
Pricing Tiers at a Glance
Leadpipe is the only identity resolution API you can start using today without talking to a sales rep - sign up, get an API key, and start querying in minutes. FullContact advertises pricing from $99/mo but requires a sales conversation to get access. Lotame offers Panorama ID through partnerships that require engagement with their team.
Mid-Market ($10K-$50K/yr)
| Provider | Typical Pricing | What You Get |
|---|---|---|
| 5x5 Data | Custom (membership) | Co-op identity graph access |
| mParticle | $50K+/yr | CDP + IDSync cross-device |
This tier is thin for standalone identity resolution. Most providers jump from sub-$1K/mo straight to enterprise pricing.
Enterprise ($50K+/yr)
| Provider | Typical Pricing | What You Get |
|---|---|---|
| LiveRamp | $50K+/yr | AbiliTec authenticated graph |
| Experian/Tapad | $50K+/yr | Bureau-grade + cross-device |
| TransUnion/Neustar | $50K+/yr | TruAudience bureau-grade |
| Amperity | $200K+/yr | CDP with 45-algorithm matching |
| Informatica | $200K+/yr | MDM suite |
Enterprise pricing is opaque by design. These vendors want to price based on your specific data volume and use cases. Expect 3-6 month sales cycles and multi-week implementations. If you’re a startup or SMB, these are not realistic options.
The gap between the self-serve tier ($99-$147/mo) and the enterprise tier ($50K+/yr) used to be enormous. Leadpipe bridges it: at high volume (1M+ identifications/month), pricing stabilizes at approximately $8,000/month - roughly $96K/year for nearly unlimited volume. Compare that to LiveRamp’s $50K+ for far fewer identifications or Experian’s custom enterprise contracts. The cost per identification drops from $0.29 (Starter) to ~$0.008 (high-volume) - less than a penny per identified visitor, with the same 100+ data point deterministic profiles and intent signals included.
This is partly why identity data as a service - API-first, self-serve, usage-based pricing - is growing so fast. Most companies don’t need a $200K platform. They need an API endpoint and a reasonable monthly bill.
FAQ
What’s the difference between identity resolution and contact enrichment?
Identity resolution starts with an unknown signal (an anonymous website visit, a device ID, a cookie) and resolves it to a known person. Contact enrichment starts with a known person (an email address) and adds more data about them. Think of identity resolution as “who is this?” and enrichment as “tell me more about this person.” Some providers like Leadpipe do both - they resolve the unknown visitor AND return enriched data in one API call. Others like FullContact only do enrichment. For a deeper explanation, read What Is Identity Resolution.
Why do match rates vary so much between providers?
Match rates depend on three things: the size of the identity graph, the matching methodology, and how “match rate” is defined. FullContact measuring enrichment hit rates against submitted emails is a completely different metric than Leadpipe measuring the percentage of anonymous website visitors resolved to real people. Enterprise providers often don’t publish match rates at all because they vary so much by data quality and use case. The only honest way to compare is to run your own test with your actual data.
Can I use multiple identity resolution APIs together?
Yes, and many teams do. The most common pattern is using Leadpipe for visitor identification (discovering unknown visitors) and FullContact or a contact database for supplementary enrichment. You can also use Leadpipe’s API alongside Clay for waterfall enrichment. The key is understanding what each tool does well and not paying for overlapping capabilities.
Is deterministic matching always better than probabilistic?
For B2B sales and marketing, yes - almost always. When you’re sending outreach emails or making sales calls, accuracy matters more than coverage. Sending a personalized email to the wrong person is worse than not sending it at all. Probabilistic matching has its place in ad-tech (where you’re showing ads to segments, not individuals) and in large-scale consumer marketing. But for B2B identity resolution, deterministic matching gives you the confidence to act on the data.
How do I evaluate identity resolution APIs for my specific use case?
Start with three questions: (1) What signal am I starting with? (anonymous visits, email addresses, device IDs), (2) What data do I need back? (contact info, firmographics, intent signals), and (3) What’s my budget? Those three answers will eliminate 70% of the options. Then run a proof-of-concept with 2-3 finalists using your actual data. Published match rates are marketing numbers - your real-world results depend on your traffic quality, geographic mix, and ICP. Leadpipe offers a free trial with 500 leads so you can test with real data before committing.
The Bottom Line
The identity resolution market in 2026 is split into two worlds: self-serve APIs that you can start using in minutes, and enterprise platforms that take months to deploy and cost more than some companies’ entire marketing budget.
For most B2B teams, the decision is simpler than the market makes it look. If you want to identify anonymous website visitors with intent data, Leadpipe is the only truly self-serve option that combines visitor identification, person-level intent, and a proper developer experience (SDK, MCP, webhooks) at $147/mo. No sales call. No partnership agreement. Just sign up, get an API key, and start querying. If you want to enrich existing contacts, FullContact does that well (advertised from $99/mo, though you’ll need to contact their team for access).
The enterprise providers - LiveRamp, Experian, TransUnion - are legitimate but serve a different market. If you’re not at the scale where $50K+/yr is a rounding error, they’re not the right fit.
Don’t overthink it. Pick the tool that matches your starting signal (anonymous visits vs. known contacts), your budget, and your technical requirements. Then test it with real data.
Ready to see what identity resolution actually looks like? Leadpipe gives you 500 free identified leads - person-level data with intent signals, delivered through a real API. No sales call. No annual contract. Just data.
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Related Articles
- What Is Identity Resolution and Why Does It Matter?
- Deterministic vs Probabilistic Matching Explained
- Visitor Identification API: Complete Developer Guide
- Identity Resolution for Platforms: Build vs Buy vs Embed
- Identity Data as a Service: API-First Visitor Identification
- Best Contact Enrichment APIs in 2026
- Add Identity Resolution to Your SaaS in 10 Minutes
