When updating a website's CSS, browsers may continue to cache the outdated version, resulting in rendering issues. This article explores several methods to force a refresh of the cached CSS.
To resolve the caching issue, consider the following options:
What are We Trying to Achieve?
The ideal caching behavior involves fetching a new resource the first time it is requested and retrieving it from the local cache thereafter until it expires.
Observed Caching Behavior
To understand the caching behavior of browsers, a table summarizes various scenarios and their observed results.
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Cache Headers | Observed Result | ||||||||||||||||||||||||||||||
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Static filename | Expiration 1 Year | Taken from cache | ||||||||||||||||||||||||||||||
Static filename | Expire immediately | Never caches | ||||||||||||||||||||||||||||||
Static filename | None | HTTP 304 (not modified) | ||||||||||||||||||||||||||||||
Static query string | Expiration 1 Year | HTTP 304 (not modified) | ||||||||||||||||||||||||||||||
Static query string | Expire immediately | HTTP 304 (not modified) | ||||||||||||||||||||||||||||||
Static query string | None | HTTP 304 (not modified) | ||||||||||||||||||||||||||||||
Random query string | Expiration 1 Year | Never caches | ||||||||||||||||||||||||||||||
Random query string | Expire immediately | Never caches | ||||||||||||||||||||||||||||||
Random query string | None | Never caches |
Query String
Appending a random parameter to the CSS URL forces a new HTTP 200 request, but only during the initial encounter. Subsequent requests may still return 304s.
Path Modification
Creating a new path provides a more permanent solution. You can automate the process to rewrite the path with a version number or other identifier.
File Renaming
An alternative approach involves renaming the CSS files with each release, ensuring a fresh request when the updated paths are referenced in the HTML.
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