Reverse Email Lookup

Turn an email address (or phone number) into the person behind it — LinkedIn profile, name, and full enriched identity.

Normal enrichment goes person → contact info. Reverse lookup runs the other way: give Fiber an email address and get back the person's LinkedIn profile and personal details — name, headline, current company, location, and the full enriched profile shape.

There's also a reverse phone lookup: given a phone number, find the person (or company) it belongs to. Mobile and home phones typically resolve to people, while front-desk or business lines may resolve to companies.

How it works

Reverse Email Lookup stands on years of enrichment at scale: one of the largest verified email↔identity maps in the industry, paired with proprietary matching that resolves emails to real people inside Fiber's own data. That combination is what delivers the numbers below.

Performance you can expect:

70%+ hit rate on work emails: a large majority of work emails resolve to a profile.
High throughput: up to 3,500 requests/minute on the standard lookup and 3,000/minute on lite, built for backfilling a whole CRM.

Variants

Variant	Operation	When to use	Credits (on a hit)	Rate limit	Timeout
Standard	`reverseEmailLookup`	One email, full personal details	2	3,500/min	60s
Lite (high-volume)	`liteReverseEmailLookup`	Maximum throughput at lower cost; returns the essential profile match	1	3,000/min	30s
Reverse phone	`reversePhoneLookup`	A phone number → person or company	3	600/min	30s

Every variant takes one email or phone per request. For a large list, run requests in parallel within the rate limit: at Lite's 3,000 requests per minute, 100,000 emails clear in about 33 minutes.

What comes back

A match: the person's LinkedIn profile and the full enriched profile shape. Reverse phone can also return a company when the number is a business line. Neither returns contact details; send the match to Contact Reveal for emails and phones.
No match: an empty result, not an error, and no charge.
A rejected email: disposable or anonymous addresses, role-based mailboxes (info@, sales@), mailing lists, and similar addresses that don't belong to one person come back with a rejection whose reason says why. There's no person to find, so these aren't charged either.

Only have a hashed email? If your data arrives as SHA-256, MD5, or SHA-1 digests, use Hashed Email Lookup to recover the address and LinkedIn profile first.

Why teams use it

Signup-list enrichment. Turn product signups (you already have their emails) into full profiles with firmographics and titles for segmentation.
CRM backfill. Resolve the half of your CRM that only has an email into LinkedIn URLs and enriched records.
Lead routing & scoring. Resolve inbound emails to profiles in real time so routing rules and scoring models can use company size, industry, seniority.

Hashed email lookup

If you only hold hashed emails (common in ad-tech audience files and privacy-safe data shares), send up to 100 SHA-256, MD5 or SHA-1 hashes per request and we resolve them back to the address and LinkedIn profile, without you ever handling raw emails.

Each hash comes back with a status: found (with originalEmail, linkedinUrl and linkedinUserID), not_found, or rejected with a message. The call returns 200 even when some hashes miss.

{
  "apiKey": "sk_live_xxx",
  "hashedEmails": [
    "b4c9a289323b21a01c3e940f150eb9b8c542587f1abfd8f0e1cc1ffc5e475514"
  ]
}

2 credits per resolved hash; not_found and rejected hashes are free. 600 requests/minute.

Using it effectively

Have more than just an email? If you also know the person's name, company, or anything else, use the Kitchen Sink profile resolver instead — it accepts all available signals and produces better matches. Same logic applies to phone numbers: with extra context, prefer Kitchen Sink.

Pick lite for scale, single for depth. Lite trades a little match depth for speed and cost — ideal when processing tens of thousands of emails and a slightly lower hit rate is acceptable. Use the standard variant when every match matters more than marginal cost.
Pace your requests evenly. To avoid HTTP 429s, space requests out (e.g., run at roughly 1/60th of the per-minute limit per second) instead of bursting everything at once.
Work emails beat personal emails. Coverage is strongest for professional addresses; expect more misses on disposable or very old personal domains.
Know what's billed. Standard lookups bill hits (a completed miss bills emailToLinkedinMiss, free at default pricing); inputs rejected up front (disposable, role-based and similar) are free. Lite bills hits only, with misses refunded. Hashed and phone lookups bill only hits. See Cost.

Cost

Lookup	Price	What's billed
Reverse email lookup	2 credits per hit	A completed miss bills `emailToLinkedinMiss` (free at default pricing). Rejected inputs and addresses we already know don't resolve are free.
Reverse email lookup (lite)	1 credit per hit	Only hits; misses are refunded.
Hashed email lookup	2 credits per resolved hash	Only `found` hashes.
Reverse phone lookup	3 credits per number found	Only hits. Invalid numbers and misses are free.

The chargeInfo on every response is what you were actually charged; see Billing & credits.