Claude

By Anthropic. No UTM value documented yet.

What works today

Links Claude writes in the answer text on claude.ai send https://claude.ai/ as the referrer: the origin only, with no conversation path. Sites that read the referrer can already count those visits as Claude.

As of 2026-10-20.

Status

Rows are tests, columns are surfaces. Select a cell to see each link location, the date, the method and the evidence. Reported means a third-party report we have not yet verified first-hand. See how we test.

Test
claude.ai web
iOS app
Android app
macOS app
Windows app
Claude in Chrome
REF-01 Referrer present

Partial (2026-10-20)

  • Inline citation in an answer: Missing · 2026-10-20 · Verified (manual) · Chrome 155.0.8059.85 / macOS 27.2. document.referrer: (none) Landing URL: https://httpwg.org/specs/rfc9110.html Clicked an inline citation chip ("httpwg"); document.referrer was empty on the landing page. Data
  • Sources / citations panel, Deep research / research report, Canvas / document / artifact view, Link or URL written in answer text, Shared conversation page (public share link): Works · 2025-05-26 · Reported. Ahrefs: "Claude seems to have the referrer for all the links in all the areas I tested." Source Data
  • Link the user pasted, echoed back: Works · 2026-10-20 · Verified (manual) · Chrome 155.0.8059.85 / macOS 27.2. document.referrer: https://claude.ai/ Landing URL: https://main--attribution-now--keepthebyte.aem.page/t/ref-01 The link has target="_blank" and no rel. In the automated browser the new tab opened outside the test tab group, so the link was opened in the same tab (target removed); target does not change the referrer. Data

Reported: missing (2026-04-21)

  • All link locations: Missing · 2026-04-21 · Reported. Native app passed no referrer (WISLR test, April 12, 2026). Source Data

Reported: missing (2026-04-21)

  • All link locations: Missing · 2026-04-21 · Reported. Native app passed no referrer (WISLR test, April 12, 2026). Source Data

Reported: missing (2026-04-21)

  • All link locations: Missing · 2026-04-21 · Reported. Native app passed no referrer (WISLR test, April 12, 2026). Source Data

Reported: missing (2026-04-21)

  • All link locations: Missing · 2026-04-21 · Reported. Native app passed no referrer (WISLR test, April 12, 2026). Source Data

Untested

  • Inline citation in an answer, Link or URL written in answer text, Link the user pasted, echoed back: Untested.
REF-02 No full-URL leak

Works (2026-10-20)

  • Inline citation in an answer: n/a · 2026-10-20 · Verified (manual) · Chrome 155.0.8059.85 / macOS 27.2. No referrer is sent, so nothing can leak. Data
  • Sources / citations panel, Deep research / research report, Canvas / document / artifact view, Link or URL written in answer text, Shared conversation page (public share link): Untested.
  • Link the user pasted, echoed back: Works · 2026-10-20 · Verified (manual) · Chrome 155.0.8059.85 / macOS 27.2. document.referrer: https://claude.ai/ Origin only; no conversation path or ID. Data

Untested

  • Inline citation in an answer, Sources / citations panel, Deep research / research report, Link or URL written in answer text, Link the user pasted, echoed back: Untested.

Untested

  • Inline citation in an answer, Sources / citations panel, Deep research / research report, Link or URL written in answer text, Link the user pasted, echoed back: Untested.

Untested

  • Inline citation in an answer, Sources / citations panel, Deep research / research report, Canvas / document / artifact view, Link or URL written in answer text, Link the user pasted, echoed back: Untested.

Untested

  • Inline citation in an answer, Sources / citations panel, Deep research / research report, Canvas / document / artifact view, Link or URL written in answer text, Link the user pasted, echoed back: Untested.

Untested

  • Inline citation in an answer, Link or URL written in answer text, Link the user pasted, echoed back: Untested.
REF-03 Link markup (web only)

Partial (2026-10-20)

  • Inline citation in an answer: Missing · 2026-10-20 · Verified (manual) · Chrome 155.0.8059.85 / macOS 27.2. Citation chips use rel="noopener noreferrer". Data
  • Sources / citations panel, Deep research / research report, Canvas / document / artifact view, Shared conversation page (public share link): Untested.
  • Link or URL written in answer text: Works · 2026-10-20 · Verified (manual) · Chrome 155.0.8059.85 / macOS 27.2. Links written in the answer text (incl. the "Sources" list) have no rel attribute; the page policy is strict-origin-when-cross-origin. Data
  • Link the user pasted, echoed back: Works · 2026-10-20 · Verified (manual) · Chrome 155.0.8059.85 / macOS 27.2. No rel attribute; page policy strict-origin-when-cross-origin. Data
n/a
n/a
n/a
n/a

Untested

  • Inline citation in an answer, Link or URL written in answer text, Link the user pasted, echoed back: Untested.
UTM-01 UTM present

Missing (2026-10-20)

  • Inline citation in an answer: Missing · 2026-10-20 · Verified (manual) · Chrome 155.0.8059.85 / macOS 27.2. Landing URL: https://httpwg.org/specs/rfc9110.html No utm_* parameter on citation links. Data
  • Sources / citations panel, Deep research / research report, Canvas / document / artifact view, Shared conversation page (public share link): Missing · 2026-06-22 · Reported. Seer Interactive: Claude "still doesn't append UTM parameters by default"; visits arrive as claude.ai / referral. Source Data
  • Link or URL written in answer text: Missing · 2026-10-20 · Verified (manual) · Chrome 155.0.8059.85 / macOS 27.2. No utm_* parameter on links in the answer text. Data
  • Link the user pasted, echoed back: Missing · 2026-10-20 · Verified (manual) · Chrome 155.0.8059.85 / macOS 27.2. Echoed links carry no utm_* parameter. Data

Reported: missing (2026-04-21)

  • All link locations: Missing · 2026-04-21 · Reported. Native app passed no UTM (WISLR test, April 12, 2026). Source Data

Reported: missing (2026-04-21)

  • All link locations: Missing · 2026-04-21 · Reported. Native app passed no UTM (WISLR test, April 12, 2026). Source Data

Reported: missing (2026-04-21)

  • All link locations: Missing · 2026-04-21 · Reported. Native app passed no UTM (WISLR test, April 12, 2026). Source Data

Reported: missing (2026-04-21)

  • All link locations: Missing · 2026-04-21 · Reported. Native app passed no UTM (WISLR test, April 12, 2026). Source Data

Untested

  • Inline citation in an answer, Link or URL written in answer text, Link the user pasted, echoed back: Untested.
MRG-01 Keeps existing query

Works (2026-10-20)

  • Inline citation in an answer, Sources / citations panel, Deep research / research report, Canvas / document / artifact view, Link or URL written in answer text, Shared conversation page (public share link): Untested.
  • Link the user pasted, echoed back: Works · 2026-10-20 · Verified (manual) · Chrome 155.0.8059.85 / macOS 27.2. ?a=1&b=2 intact (no tag is added, so the link is unchanged). Data

Untested

  • Inline citation in an answer, Sources / citations panel, Deep research / research report, Link or URL written in answer text, Link the user pasted, echoed back: Untested.

Untested

  • Inline citation in an answer, Sources / citations panel, Deep research / research report, Link or URL written in answer text, Link the user pasted, echoed back: Untested.

Untested

  • Inline citation in an answer, Sources / citations panel, Deep research / research report, Canvas / document / artifact view, Link or URL written in answer text, Link the user pasted, echoed back: Untested.

Untested

  • Inline citation in an answer, Sources / citations panel, Deep research / research report, Canvas / document / artifact view, Link or URL written in answer text, Link the user pasted, echoed back: Untested.

Untested

  • Inline citation in an answer, Link or URL written in answer text, Link the user pasted, echoed back: Untested.
MRG-02 Keeps fragment

Works (2026-10-20)

  • Inline citation in an answer, Sources / citations panel, Deep research / research report, Canvas / document / artifact view, Link or URL written in answer text, Shared conversation page (public share link): Untested.
  • Link the user pasted, echoed back: Works · 2026-10-20 · Verified (manual) · Chrome 155.0.8059.85 / macOS 27.2. #section-2 intact (no tag is added). Data

Untested

  • Inline citation in an answer, Sources / citations panel, Deep research / research report, Link or URL written in answer text, Link the user pasted, echoed back: Untested.

Untested

  • Inline citation in an answer, Sources / citations panel, Deep research / research report, Link or URL written in answer text, Link the user pasted, echoed back: Untested.

Untested

  • Inline citation in an answer, Sources / citations panel, Deep research / research report, Canvas / document / artifact view, Link or URL written in answer text, Link the user pasted, echoed back: Untested.

Untested

  • Inline citation in an answer, Sources / citations panel, Deep research / research report, Canvas / document / artifact view, Link or URL written in answer text, Link the user pasted, echoed back: Untested.

Untested

  • Inline citation in an answer, Link or URL written in answer text, Link the user pasted, echoed back: Untested.
MRG-03 No overwrite

Untested

  • Inline citation in an answer, Sources / citations panel, Deep research / research report, Canvas / document / artifact view, Link or URL written in answer text, Link the user pasted, echoed back, Shared conversation page (public share link): Untested.

Untested

  • Inline citation in an answer, Sources / citations panel, Deep research / research report, Link or URL written in answer text, Link the user pasted, echoed back: Untested.

Untested

  • Inline citation in an answer, Sources / citations panel, Deep research / research report, Link or URL written in answer text, Link the user pasted, echoed back: Untested.

Untested

  • Inline citation in an answer, Sources / citations panel, Deep research / research report, Canvas / document / artifact view, Link or URL written in answer text, Link the user pasted, echoed back: Untested.

Untested

  • Inline citation in an answer, Sources / citations panel, Deep research / research report, Canvas / document / artifact view, Link or URL written in answer text, Link the user pasted, echoed back: Untested.

Untested

  • Inline citation in an answer, Link or URL written in answer text, Link the user pasted, echoed back: Untested.
MRG-04 Signed URLs untouched

Untested

  • Inline citation in an answer, Sources / citations panel, Deep research / research report, Canvas / document / artifact view, Link or URL written in answer text, Link the user pasted, echoed back, Shared conversation page (public share link): Untested.

Untested

  • Inline citation in an answer, Sources / citations panel, Deep research / research report, Link or URL written in answer text, Link the user pasted, echoed back: Untested.

Untested

  • Inline citation in an answer, Sources / citations panel, Deep research / research report, Link or URL written in answer text, Link the user pasted, echoed back: Untested.

Untested

  • Inline citation in an answer, Sources / citations panel, Deep research / research report, Canvas / document / artifact view, Link or URL written in answer text, Link the user pasted, echoed back: Untested.

Untested

  • Inline citation in an answer, Sources / citations panel, Deep research / research report, Canvas / document / artifact view, Link or URL written in answer text, Link the user pasted, echoed back: Untested.

Untested

  • Inline citation in an answer, Link or URL written in answer text, Link the user pasted, echoed back: Untested.

Lab-wide

Test
All surfaces
UTM-02 UTM consistent
Untested
UTM-03 UTM documented

Reported: missing (2026-06-22)

  • All link locations: Missing · 2026-06-22 · Reported. No UTM value is added, so none is documented (Seer Interactive). A feature request (anthropics/claude-code#43398) was filed in the Claude Code repo and auto-closed there as off-topic, not reviewed as a product decision. Source Data
OPS-01 Changelog
Untested

Next improvements

Each card has two prompts you can paste: one for a coding assistant working in your codebase, one to file a ticket.

Title

Add a documented UTM tag

Surfaces
claude.ai web, iOS app, Android app, macOS app, Windows app, Claude in Chrome
Tests
UTM-01, UTM-02, UTM-03
Summary
Claude links carry no UTM tag, so visits from the apps, where no referrer is possible, arrive as Direct.
Suggested fix
Add one stable utm_source value (for example claude.ai) to outbound links on every surface with a safe merge, and publish the value in the Help Center.
Copy prompt: fix in your coding harness
You are working in the codebase for Claude (claude.ai web, iOS app, Android app, macOS app, Windows app, Claude in Chrome).

Goal: improve attribution on outbound links so websites can see visits came from Claude.

Current behavior (as of 2026-10-20, manual test):
Claude links carry no UTM tag, so visits from the apps, where no referrer is possible, arrive as Direct.

Target behavior:
- UTM-01: Landing URL contains `utm_source=claude.ai`.
- UTM-02: Same `utm_source` value on every surface and link location.
- UTM-03: Value published in the lab's public docs/help.

Implementation guidance:
- Find where outbound links are rendered or opened for: inline citation in an answer; sources / citations panel; deep research / research report; canvas / document / artifact view; link or URL written in answer text; link the user pasted, echoed back; shared conversation page (public share link).
- Web: remove `noreferrer` from citation links; keep `noopener`; set referrer policy to `origin` or `strict-origin-when-cross-origin`. Avoid `window.open(url, "_blank", "noopener,noreferrer")`.
- Add `utm_source=claude.ai` (a suggested value; choose one stable value and publish it) using safe merging: keep existing query and fragment, never overwrite existing utm_* params, skip signed/expiring URLs.
- Native apps: open links so the platform passes what it can (Android Custom Tabs with an app referrer); rely on the UTM where no referrer is possible.
- Add tests using these vectors: https://attribution.now/tests#test-vectors

Verify by opening https://attribution.now/t/check from each changed surface; the page shows the referrer and UTM it received.

Reference: https://attribution.now/best-practices
Copy prompt: file a ticket
Create a ticket in our tracker for the following.

Title: Add a documented UTM tag
Component: claude.ai web, iOS app, Android app, macOS app, Windows app, Claude in Chrome — outbound links
Type: Improvement
Summary: Claude links carry no UTM tag, so visits from the apps, where no referrer is possible, arrive as Direct.
Current behavior: as of 2026-10-20 (manual test).
Why it matters: Websites receiving visits from Claude count them as "Direct" traffic when no referrer or UTM arrives, which hides the value Claude sends to publishers and brands.
Acceptance criteria:
- [ ] UTM-01: Landing URL contains `utm_source=claude.ai`.
- [ ] UTM-02: Same `utm_source` value on every surface and link location.
- [ ] UTM-03: Value published in the lab's public docs/help.
Verification: open https://attribution.now/t/check from claude.ai web, iOS app, Android app, macOS app, Windows app, Claude in Chrome and confirm the referrer/UTM shown.
References: https://attribution.now/labs/anthropic-claude · https://attribution.now/best-practices
Title

Send the claude.ai referrer from citation chips

Surfaces
claude.ai web
Tests
REF-01, REF-03
Summary
Links in the answer text already send the claude.ai referrer, but the inline citation chips use rel="noopener noreferrer", so clicks on citations arrive with no referrer and count as Direct.
Suggested fix
Drop noreferrer from the citation chip component and keep noopener, matching links in the answer text. The page's strict-origin-when-cross-origin policy keeps it to the origin.
Copy prompt: fix in your coding harness
You are working in the codebase for Claude (claude.ai web).

Goal: improve attribution on outbound links so websites can see visits came from Claude.

Current behavior (as of 2026-10-20, manual test):
Links in the answer text already send the `claude.ai` referrer, but the inline citation chips use `rel="noopener noreferrer"`, so clicks on citations arrive with no referrer and count as Direct.

Target behavior:
- REF-01: Request to the target carries `Referer` with the assistant's origin (e.g. `https://chatgpt.com/`).
- REF-03: Citation links use `noopener` without `noreferrer`; page/link referrer policy is `origin` or `strict-origin-when-cross-origin`.

Implementation guidance:
- Find where outbound links are rendered or opened for: inline citation in an answer.
- Web: remove `noreferrer` from citation links; keep `noopener`; set referrer policy to `origin` or `strict-origin-when-cross-origin`. Avoid `window.open(url, "_blank", "noopener,noreferrer")`.
- Add `utm_source=claude.ai` (a suggested value; choose one stable value and publish it) using safe merging: keep existing query and fragment, never overwrite existing utm_* params, skip signed/expiring URLs.
- Native apps: open links so the platform passes what it can (Android Custom Tabs with an app referrer); rely on the UTM where no referrer is possible.
- Add tests using these vectors: https://attribution.now/tests#test-vectors

Verify by opening https://attribution.now/t/check from each changed surface; the page shows the referrer and UTM it received.

Reference: https://attribution.now/best-practices
Copy prompt: file a ticket
Create a ticket in our tracker for the following.

Title: Send the claude.ai referrer from citation chips
Component: claude.ai web — outbound links
Type: Improvement
Summary: Links in the answer text already send the `claude.ai` referrer, but the inline citation chips use `rel="noopener noreferrer"`, so clicks on citations arrive with no referrer and count as Direct.
Current behavior: as of 2026-10-20 (manual test).
Why it matters: Websites receiving visits from Claude count them as "Direct" traffic when no referrer or UTM arrives, which hides the value Claude sends to publishers and brands.
Acceptance criteria:
- [ ] REF-01: Request to the target carries `Referer` with the assistant's origin (e.g. `https://chatgpt.com/`).
- [ ] REF-03: Citation links use `noopener` without `noreferrer`; page/link referrer policy is `origin` or `strict-origin-when-cross-origin`.
Verification: open https://attribution.now/t/check from claude.ai web and confirm the referrer/UTM shown.
References: https://attribution.now/labs/anthropic-claude · https://attribution.now/best-practices
Title

Pass an app referrer from the Android app

Surfaces
Android app
Tests
REF-01
Summary
The Android app sends no referrer, so tools that rely on the referrer see Direct even when Claude sent the visit.
Suggested fix
Open links in a Custom Tab and set Intent.EXTRA_REFERRER to android-app://com.anthropic.claude, so the browser can pass an app referrer.
Copy prompt: fix in your coding harness
You are working in the codebase for Claude (Android app).

Goal: improve attribution on outbound links so websites can see visits came from Claude.

Current behavior (as of 2026-04-21, third-party report, not yet verified by attribution.now):
The Android app sends no referrer, so tools that rely on the referrer see Direct even when Claude sent the visit.

Target behavior:
- REF-01: Request to the target carries `Referer` with the assistant's origin (e.g. `https://chatgpt.com/`).

Implementation guidance:
- Find where outbound links are rendered or opened for: inline citation in an answer; sources / citations panel; deep research / research report; link or URL written in answer text; link the user pasted, echoed back.
- Web: remove `noreferrer` from citation links; keep `noopener`; set referrer policy to `origin` or `strict-origin-when-cross-origin`. Avoid `window.open(url, "_blank", "noopener,noreferrer")`.
- Add `utm_source=claude.ai` (a suggested value; choose one stable value and publish it) using safe merging: keep existing query and fragment, never overwrite existing utm_* params, skip signed/expiring URLs.
- Native apps: open links so the platform passes what it can (Android Custom Tabs with an app referrer); rely on the UTM where no referrer is possible.
- Add tests using these vectors: https://attribution.now/tests#test-vectors

Verify by opening https://attribution.now/t/check from each changed surface; the page shows the referrer and UTM it received.

Reference: https://attribution.now/best-practices
Copy prompt: file a ticket
Create a ticket in our tracker for the following.

Title: Pass an app referrer from the Android app
Component: Android app — outbound links
Type: Improvement
Summary: The Android app sends no referrer, so tools that rely on the referrer see Direct even when Claude sent the visit.
Current behavior: as of 2026-04-21 (third-party report, not yet verified by attribution.now).
Why it matters: Websites receiving visits from Claude count them as "Direct" traffic when no referrer or UTM arrives, which hides the value Claude sends to publishers and brands.
Acceptance criteria:
- [ ] REF-01: Request to the target carries `Referer` with the assistant's origin (e.g. `https://chatgpt.com/`).
Verification: open https://attribution.now/t/check from Android app and confirm the referrer/UTM shown.
References: https://attribution.now/labs/anthropic-claude · https://attribution.now/best-practices
Title
Surfaces
claude.ai web, iOS app, Android app, macOS app, Windows app, Claude in Chrome
Tests
OPS-01
Summary
There is no public note on how Claude links are attributed, so sites can't tell a product change from a traffic change.
Suggested fix
Add a short Help Center page on link attribution (referrer, UTM value once added) with dated updates.
Copy prompt: fix in your coding harness
You are working in the codebase for Claude (claude.ai web, iOS app, Android app, macOS app, Windows app, Claude in Chrome).

Goal: improve attribution on outbound links so websites can see visits came from Claude.

Current behavior (as of no test data yet, untested):
There is no public note on how Claude links are attributed, so sites can't tell a product change from a traffic change.

Target behavior:
- OPS-01: Lab publishes link-behavior changes (help page, release notes).

Implementation guidance:
- Find where outbound links are rendered or opened for: inline citation in an answer; sources / citations panel; deep research / research report; canvas / document / artifact view; link or URL written in answer text; link the user pasted, echoed back; shared conversation page (public share link).
- Web: remove `noreferrer` from citation links; keep `noopener`; set referrer policy to `origin` or `strict-origin-when-cross-origin`. Avoid `window.open(url, "_blank", "noopener,noreferrer")`.
- Add `utm_source=claude.ai` (a suggested value; choose one stable value and publish it) using safe merging: keep existing query and fragment, never overwrite existing utm_* params, skip signed/expiring URLs.
- Native apps: open links so the platform passes what it can (Android Custom Tabs with an app referrer); rely on the UTM where no referrer is possible.
- Add tests using these vectors: https://attribution.now/tests#test-vectors

Verify by opening https://attribution.now/t/check from each changed surface; the page shows the referrer and UTM it received.

Reference: https://attribution.now/best-practices
Copy prompt: file a ticket
Create a ticket in our tracker for the following.

Title: Publish a changelog for link behavior
Component: claude.ai web, iOS app, Android app, macOS app, Windows app, Claude in Chrome — outbound links
Type: Improvement
Summary: There is no public note on how Claude links are attributed, so sites can't tell a product change from a traffic change.
Current behavior: as of no test data yet (untested).
Why it matters: Websites receiving visits from Claude count them as "Direct" traffic when no referrer or UTM arrives, which hides the value Claude sends to publishers and brands.
Acceptance criteria:
- [ ] OPS-01: Lab publishes link-behavior changes (help page, release notes).
Verification: open https://attribution.now/t/check from claude.ai web, iOS app, Android app, macOS app, Windows app, Claude in Chrome and confirm the referrer/UTM shown.
References: https://attribution.now/labs/anthropic-claude · https://attribution.now/best-practices

Shipped

Nothing recorded yet.

Full history on the changelog.

Last verified: 2026-10-20. Last checked: 2026-10-20.

Work on Claude and see something out of date? Request a review and we will update the entry.

title
Claude link attribution status
description
Referrer and UTM status for Claude links, by surface and link location, with next improvements.