Cookieless identity readiness

WHY THIS EXISTS

You probably have more identity in your cookies than you think.

Most product, fraud, and growth teams reach a point where a cookie has stopped being a session marker and started being a load-bearing piece of identity infrastructure. The conversion join in your funnel. The "trusted device" check on your login flow. The dedupe key in your fraud queue. The attribution stitch between landing-page click and paid signup.

None of those workflows survive a cleared cookie jar, an incognito session, a switched browser, or a privacy regime that's actively shrinking what the browser is allowed to remember. This checklist helps you find them before the gap costs you.

It's not a sales pitch. It's a checklist. If the answer is "we're fine," that's a fine answer. If it isn't, the next step is to make one hosted /identify call and decide what to do with the evidence.

PART 1 — AUDIT

Where is identity hiding?

• List every cookie set by your domain. For each one, write what would break if it disappeared mid-session. The cookies that produce a one-line answer are session state. The cookies that need a paragraph are identity infrastructure in disguise.
• Grep your codebase for document.cookie, localStorage, and sessionStorage. Anywhere a value is being read back days later, ask whether that value is uniquely identifying.
• For each analytics or attribution tool you use, find the cookie / local-storage key that holds its user id. Note which downstream workflows assume that id is stable across sessions.
• For each authentication flow, list the signals you use to decide whether a login is "from a known device." If the only signals are cookies and IP, that flow is brittle.
• For each fraud or abuse review queue, list the fields a reviewer uses to decide if two events are the same actor. If the answer is "email + IP," that's not device evidence.

PART 2 — FAILURE MODES

When does the cookie story stop working?

• The user clears their browser storage manually — at minimum, every workflow that depended on a cookie now fails open.
• The user opens a Safari or Firefox window in private/incognito mode — most cookies start blank and get discarded on close.
• The user logs in from a second device or browser — your "returning user" signal disappears.
• The user is on iOS with Intelligent Tracking Prevention — your first-party cookie lifetime may be capped at 7 days.
• The user accepts a strict consent banner — some of your scripts may not be allowed to set the cookies they previously relied on.
• The user's request passes through a redirect chain (auth provider, payment processor, CDN) — your cookies may not survive the round trip.
• The user is embedded in another product's iframe — third-party cookie restrictions may have already deleted your storage.

For each item on your audit list from Part 1, mark which of these failure modes silently breaks it. The ones with three or more checkmarks are the candidates for a device-evidence layer.

PART 3 — DECIDE

What does a visitor_id buy you?

PART 4 — INSTALL

How to test it in one afternoon.

• Create a free fingerprint.dev account. 1,000 identify requests / month, no card.
• Create one API key in the console. Add your production origin to the allowlist.
• Pick the single most painful workflow from your Part 2 list — usually the one that breaks under incognito or storage-clearing.
• Add one /identify call at the start of that workflow. Store the returned visitor_id alongside the event you already record there.
• For one week, log the difference between your existing identifier and visitor_id. The mismatches are the cases you were silently missing.
• Decide whether to extend to additional workflows, change a confidence threshold, or stop. There is no commitment beyond the call itself.

PART 5 — WHAT YOU DON'T NEED TO DO

Things this checklist is not asking of you.

• Replace your authentication system. fingerprint.dev returns evidence, not auth decisions.
• Replace your analytics distinct id. Use both. Pick one as the join key and treat the other as a cross-check.
• Migrate every cookie at once. The point is to find the load-bearing ones, not to rip out session state.
• Set up a vendor procurement process. The free tier exists so you can prove the integration before anyone asks for a card.
• Trust a confidence score blindly. Use it as a route — allow, challenge, review, or ignore — not as a verdict.

NEXT STEP

Run the checklist. Then make one call.

If you found at least one workflow above that's quietly running on a cookie that shouldn't be carrying it, the next step is to make one hosted /identify call and see what evidence comes back. Everything after that is product judgment.