We have noticed that our website Nginx access logs have quite a bit of 404 requests for very strange URLS that end in SYNC_NOT_REQUIRED

Example: - - [12/Dec/2019:22:36:29 +0000] "GET /first-dance-wedding-songs/SYNC_NOT_REQUIRED HTTP/2.0" 404 12786 "<domain redacted>/first-dance-wedding-songs/" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/64.0.3282.140 Safari/537.36 Edge/18.17763"

Some facts:

  • the pages load fine, there is no redirect after the page is loaded
  • We don't have any code on the pages that would make such a request
  • its unclear what is making these requests (see them coming from Chrome, Safari and other browsers)
  • there is nothing about this on Google, BUT, I already see Google indexing many pages that end in SYNC_NOT_REQUIRED. Just Google "SYNC_NOT_REQUIRED" in quotes. There is a page from Top Gear and may other websites.


  • Does anyone know more details?
  • Should we just do a redirect dropping SYNC_NOT_REQUIRED?

1 Answer 1


Got lucky the other day and saw this issue happening while checking our own page.

This issue seems to be happening when a user is already on the page, and one of the ad-slots is pulling in a tracking script that probably has an error. Here is the code, causing this request (grabbed from Chrome Developer Tools Network tab)

(new Image()).src = "https://tags.bluekai.com/site/29537?limit=1&id=2RqXzPfNFqo1agDYYA6nx9dH9Qj4CQn-XgoIi6xachZM";(new Image()).src = "SYNC_NOT_REQUIRED";(new Image()).src = "SYNC_NOT_REQUIRED";

We don't belive any traffic is being lost and at worst this shows up as an error in the Chrome Console.

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