FullContact

FullContact is an identity-resolution and data-enrichment company (founded 2010, Denver) that began as a developer-first contact-enrichment API and pivoted toward enterprise identity resolution around 2020. Its core API products today are Enrich (append 900+ data attributes to a person or company record from a single identifier such as email, phone, name+address, social URL, or MAID), Resolve (identity graph that stitches fragmented customer records to a persistent PersonID), Acumen (de-anonymize website traffic), and Identity Streme. The platform is built on a U.S. consumer identity graph of roughly 240-248M profiles, rebuilt biweekly from public records, voter/property data, purchase and transaction signals, with 30M+ updates per day. FullContact publishes an average match rate of 93% and uses a machine-learning "Belief Vector" confidence score that callers can tune per request to trade precision against coverage.

The sweet spot is enterprise marketing, ad-tech, and martech teams that need to unify first-party customer data and enrich it at scale, not individual developers doing ad-hoc lookups. While FullContact historically advertised a self-serve free Developer tier (100 calls/month) and a $99/month Growth tier (10,000 calls), real-world production access today is sales-gated: buyers contact sales, complete an evaluation, and sign an annual contract, with practical entry points reported around $500/month (Basic) up to $2,000/month (Premium) and $10,000+ Enterprise. Documentation is genuinely strong, clean V3 REST/JSON RPC-style endpoints, official Go/Java/Python clients, and a Postman workspace, and developers consistently call the API easy to integrate, well-documented, and stable, with sub-200ms response times suitable for real-time enrichment.

The recurring criticism is the gap between the advertised 93% match rate and field experience: multiple reviewers report effective match rates closer to 40-50% (especially outside the U.S.) and "too many false positives" on age, employment, and education attributes. Other friction points are the absence of data-freshness timestamps, a rate limit (~600 queries/min) too low for heavy batch work, and pricing that only pencils out at enterprise scale, which is why cost-sensitive teams routinely shop for cheaper alternatives. FullContact is a credible, mature identity-resolution platform for U.S.-centric enterprise use, but smaller teams and international use cases often find the economics and coverage hard to justify.