JavaScript files too large for phones
A theme or app script over 250 KB takes long to download and run, so the page is slow to respond.
Checked on: every page the audit scans · Zolvio’s check: “Large JavaScript files”
Why it costs you sales
Every script has to be downloaded, then read and run by the browser before the page responds smoothly. On a phone a very large script can keep buttons and menus sluggish well after the page appears.
How Zolvio detects it
While the page loads, Zolvio records every script it downloads and how big it is unpacked, which is what the browser has to read. A script from your theme, an app or another site that’s larger than 250 KB flags the page, and the finding lists the large scripts (up to ten) with their sizes. Shopify’s own scripts, such as checkout, Shop Pay and analytics, don’t count, and scripts from hosts that don’t share their sizes can’t be measured.
This is a direct measurement, so it’s reported on every plan, including Free and audits with AI turned off. With AI review on, the AI agent also checks it against the audit’s evidence before it reaches your issue list.
How to fix it
- Check which app or theme file each script in the finding comes from.
- Remove apps you no longer use, and ask the developer of an app you keep whether a lighter version is available.
- For theme scripts, remove code you no longer need, or ask your theme developer to split it so each page loads only what it uses.
In Zolvio: on paid plans with AI turned on, the guided fix writes these steps for your own store and theme: where to click in Shopify admin or the theme editor, or which file to open, the line to find and the code to add. Each file opens in Shopify’s code editor. Zolvio never edits your theme: you make the change, then Verify fix checks your published theme for code changes (or you mark it fixed), and later audits confirm the problem is gone.
Common questions
Why does “JavaScript files too large for phones” cost a Shopify store sales?
Every script has to be downloaded, then read and run by the browser before the page responds smoothly. On a phone a very large script can keep buttons and menus sluggish well after the page appears.
How does Zolvio detect “JavaScript files too large for phones”?
While the page loads, Zolvio records every script it downloads and how big it is unpacked, which is what the browser has to read. A script from your theme, an app or another site that’s larger than 250 KB flags the page, and the finding lists the large scripts (up to ten) with their sizes. Shopify’s own scripts, such as checkout, Shop Pay and analytics, don’t count, and scripts from hosts that don’t share their sizes can’t be measured.
How do I fix “JavaScript files too large for phones” on Shopify?
Check which app or theme file each script in the finding comes from. Remove apps you no longer use, and ask the developer of an app you keep whether a lighter version is available. For theme scripts, remove code you no longer need, or ask your theme developer to split it so each page loads only what it uses.
Related
- HighSpeedScripts that block the page from rendering
- HighSpeedToo many requests to third-party services
- CriticalSpeedSlow page load
- HighSpeedImages much larger than they’re shown
Documentation
- How audits work — What an audit scans and how findings become issues.
- Guided fixes — Step-by-step fixes written for your theme, with links into the code editor.
- Workflows — Go from an issue to its heatmap and recordings before you change anything.