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feat: Add note about JIT breaking sites / having perf impact #250

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bsmth merged 1 commit into from
Jul 31, 2026
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feat: Add note about JIT breaking sites / having perf impact #250

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12 changes: 9 additions & 3 deletions src/content/docs/reference/policies/SitePolicies.mdx
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Expand Up @@ -9,15 +9,21 @@ Defines policies scoped to specific sites.
**Compatibility:** Firefox 150, Firefox ESR 153\
**Preferences Affected:** N/A

The policy is made up of a list of rules that are evaluated in order. Each can contain:
The policy is made up of a list of rules that are evaluated in order.
Each can contain:

- `Match` which is a list of sites. An empty list or missing property means to match all sites.
- `Match` is a list of sites.
An empty list or missing property means to match all sites.
- `Exceptions` is also a list of sites which when matched bypasses this set of rules.
- `Policies` is an object defining the policies.

Currently the only supported policies are:

- `DisableJit` which when true disables the JIT engine for the site.
- `DisableJit` disables the JIT engine for the site when `true`.

> [!WARNING]
> When the JIT engine is disabled, some sites may be slow, experience breakages, and WebAssembly won't be executed.
> Be sure to scope `DisableJit` as narrowly as possible using `Match` patterns, or via exemptions using `Exceptions`.

It is important to note that a site here refers to a registerable domain so `*.example.com` is a valid site but `*.com` is not. `*` can also be used to refer to all sites.

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