1. Overview
Markdown Viewer renders Markdown files (.md, .markdown, .mdx, and optionally .txt) entirely on your device. All parsing, rendering, syntax highlighting, math typesetting and diagram drawing happen locally, using libraries bundled inside the extension package. No remote code is ever downloaded or executed.
The short version: we collect nothing. There is no account, no telemetry, and no server of ours that your documents ever touch.
2. What we collect
| Category | Collected | Notes |
|---|---|---|
| Analytics & telemetry | No | No trackers of any kind, on this site or in the extension |
| Your documents | No | Rendered in the tab; never uploaded anywhere |
| Account data | No | No accounts exist |
| Browsing history | No | The extension activates only on Markdown documents and reads nothing elsewhere |
| Crash reports | No | Bugs reach us only if you email them |
The extension is not directed at children and, in any case, collects no data from anyone. There is nothing to sell, share or transfer.
3. Data stored on your device
The extension stores the following on your device only, using the browser's standard extension storage:
| What | Where | Why |
|---|---|---|
| Settings (theme, fonts, layout, plugin toggles, shortcuts) | chrome.storage.sync | So preferences persist. If you're signed into your browser, the browser itself may sync this between your own devices, and that sync is operated by your browser vendor, not us. |
| Annotations (highlights, underlines, comments) | chrome.storage.local | So annotations reappear when you reopen the same document |
| Folder access handles & recent documents | IndexedDB (local) | So the folder sidebar and Recent list survive a reload; never synced |
| Per-site notice dismissals | chrome.storage.local | So dismissed banners stay dismissed |
We have no way to read any of this: it lives in your browser profile. Uninstalling the extension deletes all of it, and you can wipe it anytime via Settings → Maintenance → Clear caches / Reset.
4. Network access: exactly three cases, all under your control
- PlantUML rendering (off by default). If you explicitly enable it and accept the consent prompt, the text of each PlantUML code block is sent to the rendering server you configure (default: the public server at plantuml.com, over HTTPS) and an image is returned. That third-party server sees the diagram source you chose to render, nothing else. Keep the feature off, or point it at your own server, if your diagrams are sensitive.
- Link previews (off by default). If you explicitly enable them and accept the consent prompt, hovering an external link fetches that page once (without cookies or credentials) to show its title, description and icon. Results are cached in memory and discarded when the tab closes.
- Auto-refresh. When enabled, the extension periodically re-fetches the document already open in your tab (or re-reads the local file) to detect changes. It contacts no other host.
There is no fourth case. The extension never "phones home": updates are delivered by your browser's own store mechanism.
5. Permissions, in plain words
Storage: save your settings and annotations, as described above.Read data on websites: Markdown files can live anywhere (raw git hosts, wikis, cloud buckets), so the browser grants access broadly; the extension activates only on URLs or responses it can positively identify as Markdown/plain-text documents, and exits immediately on every other page without reading its content.webRequest / declarativeNetRequest: used to recognize Markdown served with a text/markdown content type and to make the browser display (rather than download) such files. Observe-only; no request is blocked or altered beyond that one content-type correction.Access to file URLs: optional and off by default; enable it in the browser's extension settings so local .md files render.
6. Changes
If a future version changes any of the above (for example, a new consent-gated network feature), this page will be updated before that version ships, with the "last updated" date revised. Material changes are also called out in the extension's built-in What's New notes.
7. Contact
Questions about privacy: support@markdownviewerextension.com · Support page