Shopify CLI theme dev preview extremely slow

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Topic summary

Developers are experiencing severe performance issues with Shopify CLI 3.x theme development preview. The local preview at http://127.0.0.1:9292/ takes approximately 15 seconds to load pages, though in-page changes reload quickly.

Key observations:

  • The shareable preview link loads significantly faster than localhost
  • Issue persists across different Node.js and Ruby versions
  • Shopify CLI 2.x performed better, with faster page refreshes and CSS updates
  • Browser-specific behavior noted: Chrome performs better than Safari on Mac, though CSS updates remain slow across browsers

Current status:

  • No solution has been found
  • Workaround: Some users are reverting to using the theme customizer preview and manually refreshing pages
  • Multiple users confirm experiencing the same problem, suggesting a systemic issue with CLI 3.x rather than individual configuration problems
Summarized with AI on November 6. AI used: claude-sonnet-4-5-20250929.
1

My Shopify CLI preview (via http://127.0.0.1:9292/) loads extremely slow. It takes about 15 seconds to load a page. Changes within a page do reload quite fast but if I navigate to a different page or fully reload the current page, it takes a long time.

If I navigate the preview via the share preview link that is generated with “shopify theme dev”, it’s much faster.

I just switched from CLI 2.x to 3.x and followed the official guide on shopify.dev. The old CLI is uninstalled and everything should fulfill the requirements.

Are there specific versions of node.js or ruby or a combination of specific versions that are known to cause such a slowdown? If not, any other ideas?

I’m on Windows 10, Shopify CLI 3.64.0, Node 20.15.1, Ruby 3.0.3p157

2 Likes
2

Was the old CLI working much better?

3

Certainly. Even the on page refresh when changing CSS was a tad quicker. And as mentioned, this is only the case for the preview via 127.0.0.1:9292. Via the sharable preview link page loads are much faster. Are these loading times normal for 3.x?

4

Did you find a solution? This is happening to me too, tried changing ruby version and everything, still very slow

1 Like
5

No, i couldn’t find a solution. It’s a shame but for now I use the preview of the customizer and manually refresh the page…

6

I have the same problem in Safari on Mac, but Chrome works better. Still very slow updates of css though, DOM updates are faster.