What is FastsApp?
Why FastsApp
WhatsApp has no official Linux app, and its web client lives in a browser tab. FastsApp is a small graphical client instead: a native WhatsApp app written in Rust with egui, speaking to WhatsApp through whatsapp-rust. It is a single native binary with no embedded browser engine, starts in well under a second, and keeps its layout close to WhatsApp Web, so nothing needs relearning.
What it does
- Your chats, kept. FastsApp links to your phone as a companion device, like WhatsApp Web. Messages are stored in one SQLite file on your disk, so history survives restarts and grows past what WhatsApp replays. Older history is fetched from the phone as you scroll.
- Sends everything usual. Text with formatting, replies, edits, reactions, pictures pasted or dropped, files, stickers, GIFs, and voice messages recorded in the app. Attachments wait in the composer so a caption can join them.
- Plays everything usual. Voice messages play in the bubble with WhatsApp’s own waveform; GIFs and animated stickers play in place, with the video and audio decoders built into the binary, so nothing needs installing.
- One name per person. Names come from your address book by default, the way your phone shows them, in chats, mentions, replies, and notifications alike; a setting switches to public names.
- Stays out of the way. Closing the window keeps messages arriving from the system tray. Notifications show the person’s or group’s picture, a click opens the chat, and muting a chat here mutes it on the phone too.
- Text you can take. Sweep any part of a message and copy it; a selection across messages copies the way the phone shares one, each line stamped with the time, the date, and the writer.
What it does not do yet
FastsApp deliberately has a limited scope:
- Calls, status posts, communities, newsletters, and group administration.
- Playing ordinary videos in the app; they open in your player. Voice messages and GIFs do play in place.
- Replying with an attachment (replying with text or a voice message works).
- Colour emoji on Windows: Segoe UI Emoji is not a bitmap font, so emoji stay monochrome there for now.
If something misbehaves, an issue should say what happened, what you expected, and roughly when, so the log in your state directory has it.
Account safety
FastsApp is an unofficial client, and WhatsApp’s terms of service do not endorse unofficial clients. FastsApp keeps its behaviour as close to WhatsApp Web as it can: it links as a companion device over WhatsApp’s own multi-device protocol, sends the same receipts a browser tab would, does not automate messages, and does nothing in bulk. Even so, use it with the understanding that WhatsApp could object; if that risk is not acceptable to you, or the account is critical, stay with the official clients.
Prior art
FastsApp speaks WhatsApp through whatsapp-rust, which grew out of the whatsmeow lineage. WhatsApp Web defines the companion-device model it follows. Fastpotify is its sibling, the same idea applied to Spotify.
FastsApp is an independent project, not affiliated with or endorsed by WhatsApp LLC or Meta. WhatsApp is a trademark of WhatsApp LLC.