Theme customisation that survives updates
Every Shopify project reaches the moment where the theme does not quite do something. What happens next decides how expensive the store is for the rest of its life.
There are good places to put a change and bad ones, and the difference is entirely about what happens when the theme updates.
Where to put a change, best to worst#
| Approach | Survives updates | Use when |
|---|---|---|
| Theme settings | Always | Anything the theme already exposes |
| A new section or block | Usually | New layout or content module |
| App block | Usually | Functionality from an app |
| A copied section, renamed | Mostly | You need a variant of an existing section |
| Editing a core template | Rarely | Last resort, documented |
| Scattered edits across files | Never | Never |
The rule that keeps a theme maintainable#
Add, do not edit. A new section you own will still be there after an update. A modified core template will conflict with every release until somebody gives up and stops updating — which is how stores end up three years behind on platform features.
Keep a CUSTOMISATIONS.md in the theme repository listing every file you touched and why. Future-you will not remember, and neither will the next developer.
Practical habits#
- Work in a Git repository with the theme, not only in the admin editor.
- Use a development theme for changes and publish deliberately.
- Prefix your own sections and snippets so they are obvious in a file list.
- Put custom CSS in one file, not sprinkled through templates.
- Before an update, diff the vendor release against your copy and review the conflicts.
When to stop customising and rebuild#
When the diff against the vendor theme is longer than the theme itself, you are maintaining a fork without admitting it. At that point a purpose-built theme is cheaper and honest about what you own.
Frequently asked questions
Can I edit theme files directly in the admin?
You can, and for a one-line fix it is fine. Anything larger belongs in version control where it can be reviewed and reverted.
How do I update a customised theme?
Take the vendor release, diff it against your version, and reapply your changes deliberately. This is only feasible if your changes are additive and documented.
Are app blocks safe?
Safer than editing templates, yes. Their risk is the app disappearing, not the theme update.
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