The following is a list of (mostly) free image editing tools, software and apps available online. It is by no means exhaustive! I will add to it as I come across new things (or at least things that are new to me)… and I’ll try to delete anything that gets out of date.
GIMP is a fantastic, free, open-source graphics editor. It can be used for photo editing, free-form drawing and much, Much, MUCH, more. It supports many different file formats. GIMP contains many painting tools (for example, Brush, Pencil, Airbrush, Clone), it supports layers and channels, Undo/Redo (which is only limited by the disk space available), has editable text layers, contains many transformation tools (including rotate, scale, shear and flip) and selection tools (for example, rectangle, rounded rectangle, ellipse). In other words, GIMP is a good alternative to Photoshop!
Paint.NET is photo/image editing software for Windows. It is user-friendly and has an intuitive interface. It supports layers, unlimited undo, special effects (e.g. blurring, sharpening, red-eye removal, distortion and noise), and a wide variety of tools for drawing shapes.
PhotoScape is a user-friendly photo editor for Windows that also allows you to fix and enhance photos and images.
Pictomio allows you to easily archive and organise your photo collection.
Photo Pos Pro
Another good free image and photo editor. However, files can only be saved at a maximum resolution of 1,024 x 2,014 pixels. (This might be too small if you want them printed professionally.) However, it does have a choice of interfaces – one for beginners (which is simpler) and one for experts.
An open-source photo editor and manager. Features include RAW processing, non-destructive editing (so you can make changes to an image without overwriting your original), professional colour management, the ability to automate repetitive tasks, to name but a few. It is also cross platform – Darktable runs on Linux, Mac OS X and Windows.
An open-source, free, portable (you can run it from a USB stick, for example) program for Windows. PhotoDemon supports layers, infinite undo, and many filters and effects. It also supports many different file formats, including .psd (photoshop) files and .ico (Windows) files.
Scribus is a powerful, open-source desktop publishing programme (like Microsoft Publisher.) With Scribus you can design your layout, typesetting and prepare your document for professional-quality printing. The aim of Scribus is to make DTP accessible to beginners without limiting the more professional functions. Available for Windows, MacOS, Linux etc.
Browser-based / Online
Photopea is an advanced image editor. It includes all of the standard image editing tools, lots of templates and supports many different file formats. Photopea’s goal is to create the most advanced and affordable image editor. There is a paid versions, which allows you to undo up to 60 edits, but even the free version allows you to undo 30 changes.
Canva is a web-based graphic design tool. Very user-friendly to use, with drag and drop design features, and a library of more than a million stock photos for you to use. With Canva you can easily create logos, posters, invitations, postcards, social media posts, business cards and much more. Canva integrates well with other platforms such as Mailchimp, Facebook, Eventbrite and so on. Canva can be accessed online in a browser, on a mobile, or downloaded for desktop. There is a free version and a pro version (with a few more added features).
Adobe Photoshop Express Editor
This brilliant browser-based image editor is actually a cut-down version of Adobe Photoshop. It is very user-friendly to use. It contains many easy options for quick fixes or adding effects to photos. However the only downside is it only supports .jpg files smaller than 16MP (and no wider than 8,191 pixels).
Another good online photo editor. It includes effects, filters, overlays and so on. You can use Pixlr X to easily create Facebook covers, profiles, Instagram stories etc.
Fotor is probably best-known for simple one-click filters and enhancements to photos. However, it does support many different image file formats and can be used to create a photo collage quickly and easily. In addition, Fotor can also be used to create social media covers and posts (For example Facebook cover, Twitter cover) with its templates.
Stencil is also a easy-to-use online graphic design tool and image editor built for business owners, social media marketers, and bloggers. Free for personal use and there are monthly plans for professional use.
LunaPic is well known for it huge range of filters and effects. It also includes basic photo editing tools, such as cropping, rotating and amending contrast etc. You can save your image or share it to your social.
Note: please read the disclaimer before downloading or using any software.