Segment Analytics.js Blocked by Ad Blockers
Quick answer
Ad blockers and browser privacy settings block client-side Segment calls, so some data loss is expected; server-side tracking or a first-party proxy reduces it.
Most likely fix: Track critical events server-side
How to fix it
Try these in order — the most common fix is first.
1. Track critical events server-side
- Send signups and purchases from your backend with a server library
- Pass the anonymousId from the browser
Did this fix it?2. Use a first-party proxy
- Serve the library and API from your own subdomain
- Follow Segment's docs on tracking blockers and privacy settings
Did this fix it?3. Measure the gap
- Compare Segment signups with database signups to see actual loss
Did this fix it?
Symptoms
Fewer events than real traffic; analytics undefined for some users.
Why it happens
- Ad blockers block segment.com requests
- Browser tracking protection (Safari, Firefox)
- Privacy extensions
This guide also covers
- segment blocked by adblock
- analytics.js not loading
- segment ad blocker
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