Knowledge Drop

What does a ChunkLoadError in the JS console mean?

Userlevel 5

Last tested: Mar 16, 2020

A "ChunkLoadError" generally means that a checksum failed for a javascript file.

These errors occur when the browser requests a JS code chunk, and receives a response whose checksum does not match the expected “integrity=…” attribute associated with the <script> tag that refers to it.

Normally this is caused by one of:

1. Corporate proxy or Antivirus which does “man in the middle” SSL spoofing to do security scans, and falsely recognizing a pattern of bytes which looks like a malware signature

2. Ad blocking software which matches a fragment of the filename as possible ad, and it truncates/omits the response

3. An intervening cache (nginx, squid, apache, etc) has cached an empty or otherwise-modified version of the script chunk, perhaps while the Looker host was temporarily unavailable/rebooting.

The names of these files generally change with each new release of Looker, so there is a fresh opportunity to encounter one of these problems before each browser successfully caches the new files. Enabling/Disabling the CDN on the Looker instance is another way to make a change to the URLs of these chunk files, which will generate different cache keys and possibly get past any of those problems.

Clearing the browser cache almost always fixes it.


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