LastPass alternatives that are 100% Open Source, no Open-Core
Adding "open-source" to "LastPass alternative" usually means you're already wary of trusting closed software — you want to audit the code holding your passwords, not just save money. Of the catalog's 3 LastPass alternatives, only 2 are 100% FOSS.
Tools that meet this intent
Alternative to 1Password, LastPass
Lightweight Rust Bitwarden server, a self-hosted alternative to 1Password.
Alternative to LastPass
Web client for KeePass vaults, a lightweight alternative to LastPass.
Why being 100% FOSS matters here
Vaultwarden is a reimplementation of the Bitwarden server — unofficial, not affiliated with the Bitwarden project, written in Rust, compatible with the official Bitwarden apps. Per the project's own documentation, it implements most of the Bitwarden API's functionality, including organizations, Sends and emergency access — features that on Bitwarden's official cloud sit behind paid plans. This is a side effect of protocol compatibility, not a stated goal of the project to bypass any commercial plan. Bitwarden (self-hosted) — the official server — does offer those same features, but its model is Open-Core, so it doesn't make this page's cut: the selection here is specifically 100% FOSS. KeeWeb is a different case: it isn't a server, it's a web/desktop client for KeePass .kdbx vaults. Self-hosting it means hosting a static app that connects to external storage of your own (Dropbox, Google Drive, your own WebDAV) — syncing depends on that backend, not on KeeWeb.
What you gain and lose versus the SaaS
It's worth being precise about what each option actually offers: Vaultwarden isn't "Bitwarden Premium for free" — it's a community-maintained compatible implementation, not the official server. And KeeWeb doesn't replace a traditional self-hosted server — without a sync backend of your own, you don't have a centralized vault reachable from any device. If you want a password server of your own with mobile apps, Vaultwarden is the piece that covers that; if you already use or want to use the KeePass format with storage you already have, KeeWeb is the piece that makes it accessible from the browser.