Mattermost Desktop App users running Windows or Linux can download dictionary definitions from a custom URL. If custom dictionaries aren’t specified, default dictionary definitions are obtained automatically from Chromium’s CDNs.
This feature is available in the Mattermost Desktop App from v4.7.1 on Windows and Linux. Custom dictionaries are not supported in the Mattermost Desktop App on macOS.
The Mattermost Desktop App uses Hunspell Dictionary definitions for Windows and Linux. For macOS, dictionary definitions are provided by Apple within the operating system itself. A quick way to access default dictionary definitions is to obtain a copy of hunspell_dictionaries.zip from the latest electron release.
Once downloaded, the dictionary definitions need to be extracted and converted to lowercase because chromium expects en-us rather than en-US…. These definitions are ready to use and would match the usage of using Chromium’s CDN ones without accessing it, but they could also be modified to fit specific needs.
Serve the files from a web server, and write down the URL to the root folder of the dictionaries for using it in the Desktop App.
Open the Mattermost Desktop App, go to … > File > Settings. Under App Options, ensure that the Check Spelling option is enabled. Below this setting there is a link named Use an alternative dictionary URL. Use this option to specify the URL to the root folder of the dictionaries, then select Save.