When the browser can't hand a download to MDM, it keeps the download itself, so nothing is lost. The extension's toolbar button then shows a red !. Click it to see what's wrong, then How to fix it brings you to the matching section below.
To check MDM's side, open Options → General in MDM and click Test browser integration.... It checks that browser integration is on, that this is the installed copy, that the browsers can find MDM, and which browsers' extension has connected; How to fix it opens the section for the first that fails.
MDM isn't installed, or browser integration isn't set up
The browser can't find the small helper program it talks to. It is registered when MDM is installed.
- Install MDM with the setup from the download page, and keep Set up browser integration ticked.
- Already installed? Open MDM, then Options → General → Test browser integration, and click Set it up if it offers to.
- The portable copy can't be connected: it writes nothing outside its own folder. Use the installed copy for browser integration. See Portable mode.
- On Linux and macOS, MDM sets browser integration up itself each time it starts: start MDM once.
- Restart the browser after setting it up.
- Zen, Helium or another browser built on Firefox or Chromium, as your only browser on Linux or macOS? Older versions of MDM set browser integration up only for the browsers they knew. Update MDM and start it once.
- Zen on Windows: Zen 1.21.15b and later have a bug of their own that keeps add-ons from reaching their helper program (zen-browser/desktop#15432), with any add-on that uses one. Until Zen fixes it, Zen 1.21.14b works.
MDM didn't start in time
When MDM isn't running, the browser starts it for each download and waits for it. It waited about 20 seconds this time and gave up.
- Start MDM yourself and try the download again.
- A first start, a slow disk, or an antivirus scanning MDM can take that long. Next time it is usually quick.
- With a VPN or proxy program, allow connections to
127.0.0.1(your own computer): the browser's helper reaches MDM through one. - If MDM never opens, see The setup or MDM won't start.
The connection to MDM failed
The browser started MDM's helper, but it stopped before answering. Security software is the usual cause.
- Allow
misterdownloadmanager-nmhost.exe(in MDM's folder) in your antivirus or anti-malware program. - Reinstall MDM to restore its files.
MDM doesn't accept this copy of the extension
MDM's helper serves only its own extension. The browser says this copy isn't one it knows.
- Two copies installed? Open the browser's extensions page (
chrome://extensions,edge://extensions,brave://extensions) and keep only one Mister Download Manager. - A copy from elsewhere? Remove it and add the extension as MDM's Add Mister Download Manager to your browser window shows (see Browser integration).
- An older MDM? Update MDM: a newer extension may have an ID an old helper doesn't know.
The extension is newer than MDM
Downloads still work, but some of the extension's features need a newer MDM. Update it with Help → Check for updates... in MDM.
A download's details were too large
A download carries its site's cookies (and a form's data) to MDM. A few sites set so many that together they exceed what MDM accepts from the browser (1 MB). The browser kept this one. Signing out and back in to the site usually trims them.
Downloads stay with the browser although MDM is connected
The extension is connected, but MDM's own settings leave this download to the browser. Check, in MDM:
- Options → General → Use advanced browser integration is on, and your browser is ticked under Capture downloads from the following browsers.
- The file's type is listed in Options → File types.
- The site isn't in Don't start downloading automatically from the following sites, nor the address in Don't start downloading automatically from the following addresses.
- The file isn't smaller than Don't take files smaller than in Options → File types.
Also check the extension's toolbar button: with Take downloads from this browser off, everything stays with the browser.
The browser opens PDFs and music instead of sending them
MDM also takes the file types the browser would show or play itself (a PDF, an MP3), when they're listed in Options → File types and Also take files the browser would open is ticked in Options → General → Keys.... This needs a Chromium browser (Chrome, Edge, Brave, Opera, Vivaldi) version 128 or later, or Firefox. Sites in MDM's excluded sites keep opening them in the browser. Hold Alt while clicking a link to leave it to the browser: Firefox then opens it, while Chromium browsers download it themselves (Alt+click is their own "download link").
The extension can't read this site
In Chrome, Edge and Brave you can limit an extension to some sites (right-click its toolbar button → This can read and change site data). On a site it may not read, the extension can't pass your sign-in on, so it leaves the download to the browser. Choose On all sites to let MDM take downloads everywhere.
Firefox forgets the extension after a restart
An add-on loaded with Load Temporary Add-on is removed when Firefox closes, so for now it has to be loaded again after each restart (see Browser integration). A signed add-on that Firefox keeps is on the way.
Linux: Flatpak and Snap browsers
Browsers installed as a Flatpak or a Snap run in a sandbox that may keep them from starting programs outside it, so they may not be able to reach MDM. Flatpak browsers (such as Zen's app.zen_browser.zen) can't start MDM's helper, so MDM doesn't list them in Add Mister Download Manager to your browser. Install the browser from your distribution's packages (or the browser maker's own .deb, .rpm, tarball or AppImage) to use browser integration.
Next steps
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