Getting "net::ERR_BLOCKED_BY_CLIENT" error on some AJAX calls

Question

Recently I've realised that, some adblocker extensions (such as adBlocker plus) block some Ajax calls. I get that error on the console:

GET http://localhost/prj/conn.php?q=users/list/ net::ERR_BLOCKED_BY_CLIENT

Why does it block some Ajax call but not the others and what causes that? Is there any workaround other than telling user to turn off adblocker?

Possible duplicate of [I am getting Failed to load resource: net::ERR\_BLOCKED\_BY\_CLIENT with Google chrome](https://stackoverflow.com/questions/22318119/i-am-getting-failed-to-load-resource-neterr-blocked-by-client-with-google-chr) — Joshua Drake, Sep 13 '17 at 18:50
I wrote a blog post and video that should shed some light on this issue. https://love2dev.com/blog/what-the-heck-does-neterr_blocked_by_client-mean-and-how-can-you-fix-it/ — Chris Love, Feb 27 '18 at 14:58
This worked. Right click on AbBlock plugin in Chrome (top right side), and click on "pause on all sites" — Manohar Reddy Poreddy, Mar 07 '19 at 14:17
Would be great to have a non assumptive answer. I'm using no ad blockers but can't seem to find a way to debug this properly. Why the browser doesn't identify the source of the block is beyond me. — Philip Ingram, Jun 02 '20 at 18:44

score 803 · Accepted Answer · answered Apr 28 '14 at 23:19

803

AdBlockers usually have some rules, i.e. they match the URIs against some type of expression (sometimes they also match the DOM against expressions, not that this matters in this case).

Having rules and expressions that just operate on a tiny bit of text (the URI) is prone to create some false-positives...

Besides instructing your users to disable their extensions (at least on your site) you can also get the extension and test which of the rules/expressions blocked your stuff, provided the extension provides enough details about that. Once you identified the culprit, you can either try to avoid triggering the rule by using different URIs, report the rule as incorrect or overly-broad to the team that created it, or both. Check the docs for a particular add-on on how to do that.

For example, AdBlock Plus has a Blockable items view that shows all blocked items on a page and the rules that triggered the block. And those items also including XHR requests.

Blockable items

answered Apr 28 '14 at 23:19

nmaier

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We had to change the api eventually but we solved it. Thanks a lot for the hint... – s.alem Jun 27 '14 at 13:14
Argh! I just spent 30 minutes or more troubleshooting other things - but this was it! :( – Will Strohl Dec 05 '14 at 02:49
1

same here. I kept changing my code and looking for the cause of this problem and it turned out to be my AdBlock was simply blocking the call that I was working on :D – Andrei Apr 14 '15 at 15:41
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after half a day of searching why delete and get won't work, found this...it's so funny we are not even mad :)) – bokkie Jul 03 '15 at 13:52
You can enable this view in Firefox with Adblock Plus plugin installed by pressing Ctrl + Shift + V. I didn't manage to open it in Chrome, but the filter list by default is the same in both browsers, so it did the trick and helped mi with finding part of url that caused AdBlock to react. – Mark Apr 11 '16 at 11:54
Was uMatrix for me. Just check your addons. – ferdynator Dec 18 '17 at 12:44
So how do you push to production something that will be blocked by AdBlocker? – Henry Lynx Apr 25 '18 at 16:57
Thanks for answer. the /api/adverts/most-recent uri was blocking by adblocker so I changed it to something else and it works. – Ozal Zarbaliyev Jan 04 '20 at 04:45
For me, I had to disable the Brave browser's shields: https://support.brave.com/hc/en-us/articles/360022973471-What-is-Shields- – Ryan Apr 09 '21 at 16:05
Such a serious issue. This means my app won't load on many people's computers. Even though I don't have any ads there, just the mention of `/img/1.gif` was blocked and the entire site was a white page. – Tamal Anwar Chowdhury Nov 10 '22 at 16:03

score 126 · Answer 2 · edited Jan 19 '17 at 20:50

126

If your URL contains words such as "advert", "ad", "doubleclick", "click", or something similar…

For example:

GET googleads.g.doubleclick.net/pagead/id
static.doubleclick.net/instream/ad_status.js

…Then ad-blocker will block it.

edited Jan 19 '17 at 20:50

2540625

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answered Oct 02 '15 at 22:11

ShapCyber

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Great. Im having a **ad**min page ;) – Servus7 Oct 23 '15 at 09:07
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In my case the problem was having a folder called "ads" with pictures that was shown in the website. I just changed the folder to "publish" and it was solved. – Francisco De La Fuente Aug 03 '16 at 15:36
I have disabled Ad Blocker for page but still getting same error – Madan Bhandari Nov 16 '16 at 12:50
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In my understanding the ad_status.js gets created when using google products such as embedded youtube videos. So is it even possible to avoid the adBlock when having this file ? – Niklas Apr 27 '17 at 15:14
wait, what , why adblocker block these url? – parlad Apr 30 '18 at 08:03
This is a major problem indeed. You saved me days of headaches, my app was called ADS and it was in the /ads folder.. – cdsaenz May 22 '19 at 19:10
Wonderful, our app is using authentication with Active Directory and can you guess what the url that's being blocked is? "ad/auth"... – Matt K Oct 29 '19 at 13:34
Wrote an article on logical fallacies. Was wondering why my _**ad**-hominem_ images were being blocked... – Deolu A Feb 28 '21 at 19:11
I had an issue with the URL including "stats" – Jeroen van Dijk Feb 25 '22 at 09:18
thank you, actually it was Mr adblocker – Temuujin Dev Jul 25 '22 at 11:22
was also happening to me in Brave browser for the word 'cookies' – Vincent Casey Apr 13 '23 at 15:15

score 52 · Answer 3 · edited Jul 11 '17 at 12:52

52

I've discovered that if the filename has 300 in it, AdBlock blocks the page and throws a ERR_BLOCKED_BY_CLIENT error.

edited Jul 11 '17 at 12:52

moritzg

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answered Aug 04 '15 at 17:13

Bill_VA

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I've confirmed this and also notified the team at unsplash.com – Tony O'Hagan Jun 17 '20 at 22:30

score 29 · Answer 4 · answered Aug 05 '22 at 11:17

29

I was facing same issue, I was using Brave Browser, disabling protection against site on which I was facing issue worked

answered Aug 05 '22 at 11:17

Sanket Patil

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Brave for me too. I always forget about that thing. It causes weird issues on sites. – Andy Oct 19 '22 at 20:34
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Holy ... Thanks a lot for you answer I was becoming crazy and that's exactly the problem I had ... ‍♂️ – Simon Trichereau Feb 08 '23 at 15:14
I can't believe it was this simple! This totally solved my problem – biogeek Aug 25 '23 at 13:04

score 22 · Answer 5 · answered Jul 07 '16 at 13:01

22

Add PrivacyBadger to the list of potential causes

answered Jul 07 '16 at 13:01

bvanlew

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I just had an issue where PrivacyBadger was blocking something. I think the reason was that the content was on a "test" subdomain. i.e. test.example.com but I'm not sure that was the reason. – krick Aug 19 '16 at 15:42
+1 , i've been trying to fix this issue for days and just after seeing this topic, i could find out Privacy Badger was the culprit – delphirules Dec 26 '21 at 11:54

MichaelMao · Answer 6 · 2020-07-21T06:21:09.113

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I find a case is if your url contains the key word banner, it will blocked too.

edited Jul 21 '20 at 06:21

answered Feb 03 '16 at 06:23

MichaelMao

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score 16 · Answer 7 · answered Dec 13 '21 at 09:38

16

I had sentry calls failing with this and disabling brave ads shield on Brave browser did solve the issue for me.

answered Dec 13 '21 at 09:38

Dimitri Kopriwa

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Thanks! I was testing and it didn't work on my phone either. Turns out I use Brave on both...now fixed – Joris Limonier Jul 14 '22 at 16:43
Thank you, thank you, thank you!!! I've spent hours on this. – Chris Johnson Dec 27 '22 at 22:10
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Additional question would be how to disable this on development? – user158 Jun 23 '23 at 02:15

score 11 · Answer 8 · edited Nov 17 '20 at 10:47

As it has been explained here, beside of multiple extensions that perform ad or script blocking you may aware that this may happen by file names as below:

Particularly in the AdBlock Plus the character string "-300x600" is causing the Failed to Load Resource ERR_BLOCKED_BY_CLIENT problem.

As shown in the picture, some of the images were blocked because of the '-300x600' pattern in their name, that particular text pattern matches an expression list pattern in the AdBlock Plus.

score 8 · Answer 9 · answered Feb 09 '22 at 08:52

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If there are any ad blockers (Brave browser use default blocker), turn it off. This worked for me

answered Feb 09 '22 at 08:52

shrikanta mazumder

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I use Vivaldi, it was the ad blockers, thanks. – Dazag Jun 30 '22 at 14:34

score 7 · Answer 10 · answered Mar 29 '21 at 03:59

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In my case, it is not the adblocker but Bitdefender anti tracker. Disable it then you all fine.

answered Mar 29 '21 at 03:59

yusufmalikul

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score 4 · Answer 11 · answered Jul 28 '22 at 03:20

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Just switching the order of some URL query params fixed the issue for me (so apparently the uBlock Origin adblocking rules are not very robust).

answered Jul 28 '22 at 03:20

Luke Hutchison

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score 2 · Answer 12 · answered Jan 07 '16 at 10:27

In my case it was a Chrome extension and Firefox add-on by Avira called "Avira Browser Safety". I had problems with version 1.7.4. In my specific case I wanted to login to a website called gliffy.com for making diagrams, but after logging in I got an blank page. If you use F12 (console) in Chrome you can see all these ERR_BLOCKED_BY_CLIENT (and other) errors.

score 2 · Answer 13 · answered Jul 18 '22 at 17:35

2

This error can also happen if you run chrome in headless mode (for example with Puppeteer or Ferrum) with a white list of URLs and the request doesn't match the list.

answered Jul 18 '22 at 17:35

Michaël Witrant

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Владимир Ефанов · Answer 14 · 2017-07-28T09:14:29.890

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Opera Blocker and others check all files/urls in Network. Then compares to the list. It is EasyPrivacy and EasyList. If your file/url in this, your will be ban. Good luck.

So... I find FilterLists for all addBlockers!

edited Jul 28 '17 at 09:14

answered Jun 14 '17 at 14:17

Владимир Ефанов

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score 0 · Answer 15 · answered Jan 28 '23 at 20:47

Thanks for the answers! They led me to a solution:

I cheated this by using a third party server that wrapped my request.
Check it out:
https://codetabs.com/cors-proxy/cors-proxy.html

GET "https://api.codetabs.com/v1/proxy?quest=your_blocked_url"

Of course, it is better to wrap it with your own server.

Getting "net::ERR_BLOCKED_BY_CLIENT" error on some AJAX calls

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