I am not sure if it is related to the Stack Exchange network, but the Developer Tools in Chrome sometimes log an Uncaught SyntaxError: JSON.parse while viewing questions on Stack Overflow. The SyntaxError is related to the file ados.js which I think belongs to adzerk.

Uncaught SyntaxError: JSON.parse
  JSON.parse @ ados.js:3
  impressionData @ ados.js:443
  root.ados_writePixel @ ados.js:753
  pixel_command__15905 @ ados?t=1439202202176&request={"Placements":[{"A":22,"S":8277,"D":"adzerk639078980","ATA":[17,2221],…:5
  root.azLoad @ ados.js:208  
  (anonymous function) @ ados?t=1439202202176&request={"Placements":[{"A":22,"S":8277,"D":"adzerk639078980","ATA":[17,2221],…:9

How to reproduce (only for those who have the New Navigation in place):

  1. Go to https://stackoverflow.com/questions/new?show=all&sort=recentlyactive
  2. Open Developer Tools F12
  3. Open a question from the List → An Uncaught SyntaxError may be written to console
  4. If no SyntaxError is logged → Navigate back by clicking on Stack Overflow icon and retry at Step 3
  • A link to the question could be useful. Or it is completely random? Aug 10, 2015 at 11:03
  • @PatrickHofman Its not a specific question. But for this question stackoverflow.com/questions/31915928/… i could reproduce it
    – Jehof
    Aug 10, 2015 at 11:07
  • That sounds like it is coming from our 3rd party ad provider, although I cannot reproduce what you are seeing; somewhat vexing, but also probably out of our hands. I wonder - is it possible this is due to local interception by a work proxy, adblock, or some other tool trying to protect you from ads? Aug 10, 2015 at 11:43
  • @MarcGravell I have no adblocker installed in Chrome. I´m not sure if my company network blocks some ads. But I think not. I will try to reproduce it from home
    – Jehof
    Aug 10, 2015 at 11:55
  • @Jehof I can repro but not consistently, and I can't isolate the cause just yet. Note I can't repro it at /questions?show=all&sort=active, only at /questions?sort=active.
    – stevvve
    Aug 10, 2015 at 13:33
  • 5
    We are digging into this on the adzerk side - it looks like a bug in our logging code that is only triggered in some instances. Once we have it resolved I will leave an answer. Aug 10, 2015 at 16:01
  • Do you remember seeing any specific ad when it happened? Might be a single "corrupted" ad. /cc @stevvve. Aug 11, 2015 at 6:48
  • @ShadowWizard There are no ads at all. The only one is from careers "Looking for a job?".
    – Jehof
    Aug 11, 2015 at 6:52
  • hmm... I see the link you posted works only for new nav. I get Page Not Found error, so can't really try and repro. Aug 11, 2015 at 6:53
  • @ShadowWizard Nope, I didn't see a connection between a specific ad and the error.
    – stevvve
    Aug 11, 2015 at 17:52

1 Answer 1


This has been fixed on our side (Adzerk, I'm the Founder and CEO) - we recently added events to our client-side JavaScript and when de-serializing some records it was failing. This was due to the fact that we use a modified BASE64 (that will work on our URLs) and we weren't correctly de-modifying it before we tried to decode it.

It didn't cause any issues - other than some console messages (which I know are annoying!)

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