Guides › Open-Source Office Software: The Complete List
Open-Source Office Software: The Complete List
Published 8/31/2026
Every open-source tool in the OfficeToolGuide directory, with what each one is actually good at. Open source means no paid tier to be upgraded into and the option to self-host.
Open source is a different proposition from a free plan. A free plan is a commercial decision the vendor can revisit; open source is a licence. There is no paid tier waiting above you, no seat count to grow into, and you can run it on your own hardware if you ever need to.
The trade is usually convenience. You may be doing your own hosting, updates and backups, and support is a community rather than a contract. That is a good deal for some teams and a bad one for others, which is why the list below says what each tool is for rather than ranking them.
The tools
Nextcloud
Organizations and privacy-focused individuals who want to self-host their own file-sync server instead of trusting a third party with data.
Category: cloud-storage Free plan includes: Fully open-source, self-hosted software is free with no storage cap of its own (limited only by your own server); paid managed/enterprise hosting (Nextcloud One, Enterprise) is separate and billed per user.
Mattermost
Self-hosted, open-source team chat for organizations (often government/regulated/dev-focused) that need to control their own data and infrastructure.
Category: communication Free plan includes: Free, self-hosted open-source edition available (community-supported, core messaging/channels); paid Professional/Enterprise tiers add SSO, compliance, AI features and support and are priced per seat, sold as annual licenses
Rocket.Chat
Self-hosted or on-prem team chat with strong compliance/data-sovereignty options, suited to government, defense and regulated industries.
Category: communication Free plan includes: Free self-managed/open-source workspace available for technical evaluation, small businesses and non-profits with core collaboration and security features; Commercial/Government/Defense tiers are quote-based via sales
draw.io (diagrams.net)
No-cost, no-account technical and flowchart diagramming that saves directly to Google Drive, OneDrive, or local files; popular for engineering/IT documentation.
Category: design-diagramming Free plan includes: Free forever, no sign-up required, no feature paywall or enterprise-only tier; open source under Apache 2.0. diagrams.net now redirects to drawio.com.
Joplin
Privacy-focused, open-source Markdown note-taking with end-to-end encrypted sync options and full data ownership.
Category: note-taking Free plan includes: Fully free and open-source on Windows, macOS, Linux, Android, iOS, and terminal, with no feature paywall; only the optional hosted Joplin Cloud sync service is paid (free alternatives like Dropbox/OneDrive sync are supported instead).
Logseq
Outliner-style networked note-taking with daily journals, backlinks, and a plugin ecosystem, popular for PKM/Zettelkasten workflows.
Category: note-taking Free plan includes: The privacy-first, open-source outliner app itself is free to use locally with local Markdown/Org files; an optional paid Logseq Sync add-on exists for cloud sync (exact current price not confirmed on the homepage).
PDFsam Basic
Users who want a free, open-source, offline desktop tool purely for splitting, merging, and rotating PDFs without any cloud upload.
Category: pdf-tools Free plan includes: PDFsam Basic is fully free and open-source (AGPL license), with no watermarks and no file-size limit; runs fully offline. Paid sibling products (PDFsam Visual, PDFsam Enhanced) add a visual editor / OCR / digital signatures via one-time purchase or subscription.
KeePassXC
Best for offices that want a completely free, offline, self-managed vault with no vendor lock-in and full source-code auditability (a cross-platform, community-maintained fork of the original KeePass).
Category: security-utilities Free plan includes: Fully free and open source (GPLv3), no cloud service, no ads, no subscriptions, no feature limits; sustained by voluntary donations.
Psono
A strong lesser-known pick for security-conscious IT teams wanting a self-hostable, open-source enterprise password manager with real team/sharing features free for small offices.
Category: security-utilities Free plan includes: All business features free for teams up to 10 users, on either self-hosted (on-premise, fully open source) or SaaS deployment; larger teams and professional support/SLAs require a custom quote.
Gnumeric
Lightweight open-source desktop spreadsheet known for fast, highly accurate numerical computation, a niche alternative to LibreOffice Calc.
Category: spreadsheets Free plan includes: Completely free and open source under GPL v2/v3, no paid tiers of any kind
ActivityWatch
Privacy-conscious users who want fully local, open-source automatic time tracking with no cloud upload of activity data.
Category: time-productivity Free plan includes: Fully free, open-source (MPL-2.0) and self-hosted with no feature limits, ads, or account requirement; all tracking data stays on-device. An optional paid 'ActivityWatch Pro' subscription (from roughly $5/month, per the site) supports development and may add extra features.
AbiWord
Minimal, fast, free open-source word processor best suited to lightweight Linux desktop use rather than full office-suite needs.
Category: word-processing Free plan includes: Entirely free and open source, no paid tiers. Current stable release is 3.0.5; distributed mainly for Linux via Flathub, with the official site noting Windows builds are currently unavailable -- an indicator of lighter ongoing development than the other suites listed here.
Apache OpenOffice
Free, long-standing open-source office suite offering a straightforward Microsoft-Office alternative for basic-to-intermediate document needs.
Category: word-processing Free plan includes: Entirely free and open source, developed by volunteers; no paid tiers. Actively maintained with periodic releases (version 4.1.16 released November 2025 per the site's own release notes).
Calligra Suite
Free, KDE-native open-source office and creative-tools suite, a natural fit for Linux desktop users already on KDE Plasma.
Category: word-processing Free plan includes: Entirely free and open source, developed by the KDE community; no paid tiers.
LibreOffice
Free, open-source desktop office suite with strong Microsoft Office file-format compatibility -- best for users who want a full-featured suite with no subscription.
Category: word-processing Free plan includes: Entirely free with no feature tiers or paywalls; funded by voluntary donations. Fully open source (MPL v2.0).
What open source does not mean
It does not automatically mean private, secure or free of running costs. A self-hosted tool is exactly as secure as the server you put it on, and hosting is not free even when the software is. It also does not mean unsupported — several tools here sell hosting or support alongside the open code.
No vendor pays to appear in this directory, and none of the links above are affiliate links.