WanMask is an extension for web browser (Chrome). You can install it locally.
You can see all releases on releases page. Download the latest one.
E.g. download https://github.com/wanchain/wanmask/releases/download/v3.0.10/wanmask-chrome-3.0.10.zip
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Goto "chrome://extensions" or open "More Tools > Extensions"
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Turn on "Developer mode"
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Click "Load unpacked" button and select the folder in step 2