Sync Theme by Dee

Automatically switches Gmail, Grafana, and Slack between light and dark to match your operating system's theme. Works only on those sites — no accounts, no tracking, no data collection. Allows custom domains for self-hosted Grafana.

Available on Firefox for Android™

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About this extension

Sync Theme keeps Gmail, Grafana, and Slack in step with your operating system's light/dark setting. Flip your OS to dark mode and your open Gmail, Grafana, and Slack tabs follow automatically — and back to light when you switch back.

Features
• Works on Gmail, Grafana (Grafana Cloud and self-hosted), and Slack web.
• A master on/off switch plus a per-site toggle, so you can run just the sites you want.
• Add self-hosted Grafana instances on your own domains — you approve each one through Firefox's permission prompt.
• No accounts, no tracking, no data collection, no remote servers.

How it works
When your OS theme changes, Sync Theme switches each site using that site's own built-in light/dark control, so it looks exactly as the site intends — including custom Slack workspace themes. It runs only on Gmail, Grafana, and Slack, never on other sites, unless you explicitly add a self-hosted Grafana domain on the options page.

Privacy
Sync Theme does not collect, transmit, or sell any data. Your on/off preferences sync through your own Firefox account; any self-hosted domains you add stay on your device. Full policy: https://github.com/sideprojects-dee/sync-theme/blob/main/PRIVACY.md

Developer comments

for named sites (Gmail, Grafana, Slack) that already support a light and dark theme but that do not auto sync this to the operating system preference... this extension watches the OS theme, and will choose the site provided light or dark theme if needed to stay in sync with the OS.

works on the most common named domains for these apps, but allows one or more custom domains to be added as Grafana specifically is OSS and can be hosted on any domain... you can use https://play.grafana.org as a test of this functionality as that domain is explicitly not included by default and is a public Grafana instance.

no data is sent anywhere, this extension is entirely self-contained.

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Sync Theme by Dee

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