Everyone needs reliable office software, and some of the very best suites are completely free – whatever operating system you use. Here, we've put the very best free office software suites through their paces – both downloadable desktop software and browser-based applications – so you can pick the one that's best for you.

1. LibreOffice

Everything you could want from an office suite, fully compatible with Microsoft formats and totally free to use – even commercially

LibreOffice is so good, you'll wonder why you ever paid for office software. It's compatible with all Microsoft document formats, and has almost every feature you'll find in the latest versions of Word, PowerPoint and Excel.

The suite contains six programs to cover every common office task: Writer, Calc, Impress, Draw, Math and Base. The last three are tools you won't find in many other free office suites, and are designed for vector diagrams, mathematical functions and databases, respectively. The latter is particularly useful; free alternatives to Microsoft Access are hard to find.

LibreOffice is an open source project maintained by a huge and enthusiastic community of volunteers constantly working to improve stability and add new features. There's a great selection of extensions and templates to make it even more flexible, and it's free for businesses as well as home users.

LibreOffice is a fork of Apache OpenOffice, and the two are extremely similar, but we’d opt for LibreOffice thanks to its more frequent update schedule and more modern interface.

LibreOffice is available for Windows, Mac and Linux, but there are no official mobile versions available except for a document viewer for Android.

2. Google Docs, Sheets and Slides

For working across platforms and sharing documents, Google's excellent collection of online office apps is hard to beat

If you work collaboratively, or switch between a PC and a Mac, Google Docs, Sheets and Slides should be your first port of call.

For anyone who's already deep into the Android/Google ecosystem, this suite will be a natural choice. The three key tools run happily in any web browser, and are available as mobile apps for Apple and Android devices.

Google's free office suite doesn't offer the advanced tools you'll find in desktop software like LibreOffice (there are no pivot tables, for example, and there's no database tool) but everything is laid out in a clear, logical way and all your files will be saved and synced automatically so you don't have to worry about transfers and backups.

The chief disadvantage of Docs, Sheets and Slides is that opening files created using other office software is a cumbersome process and files aren't always converted perfectly.

This is partly because Google's office tools use web fonts rather than ones stored locally on your device, and partly because Microsoft documents sometimes contain features not supported by Google. If that's a deal breaker for you, read on...

3. Microsoft Office Online

Microsoft is taking the fight to Google with slimmed-down versions of all its usual applications, available to use free online

Microsoft's desktop software carries a subscription fee, but the company has noticed the threat posed by G Suite and created its own set of free online apps.

Microsoft Office Online looks and works just like its desktop equivalent, and although advanced tools like pivot tables are out of reach, but aren’t offered by Google either.

If you generally use Microsoft document formats, Office Online is a brilliant choice. Unlike Google's free office suite, it doesn't need to convert your files before you can work on them, and you can share them easily through your Microsoft OneDrive account. Just log in using your Microsoft account (the same one you use to log into Windows 10) and you're ready to go.

There's a version of Office Online for Chrome, plus mobile editions of Office for iOS and Android.

4. WPS Office Free

A feature-packed free office suite for Windows, Linux and Android

WPS Office Free is a slimmed down version of a premium office suite, but you'd hardly know it. Each of its three programs looks just as slick as the latest versions of Word, Excel and PowerPoint, and is packed with just as many features.

File format support is excellent, and you can save your work in native Microsoft formats for easy sharing with Office users. There's no database software, but WPS Office comes with an excellent free PDF reader that's a great replacement for Windows' built-in app.

There's the occasional ad, but these are few and far between. They certainly won't get in the way of your work, and you'll easily forget that everything in this suite is completely free.

There are versions of WPS Office Free for Windows and Linux systems, as well as apps for Android devices, but Apple device users will need to look elsewhere.

5. SoftMaker FreeOffice 2016

A free version of a premium suite, with most pro features intact

Like WPS Office Free, SoftMaker FreeOffice provides analogs for Microsoft Word, Excel and PowerPoint (TextMaker, PlanMaker and Presentations respectively).

As with all the free office suites in this roundup, there's support for Microsoft file formats from 1997 onwards. It also offers effortless conversion to both PDF and Epub formats, which is a welcome addition.

Unfortunately, some key features are exclusive to the premium version of the software. Some of these (like tabbed browsing) are nice to have but non-essential, but the lack of a thesaurus is a real drawback for anyone who writes on a regular basis.

FreeOffice doesn't look quite as smart as WPS Office, but if you dislike the Microsoft ribbon and find it unintuitive then you'll prefer the slightly more old fashioned approach to navigation.