Big files cause small, constant problems. Photos that slow down your website. PDFs that bounce back because they are too large to email. Presentations that take forever to upload. Most of the time, the file is simply stored inefficiently. You can compress images and documents to a much smaller size without anyone noticing a difference.
We built Squish, a free file compressor, to make that easy. This guide covers what “lossless” really means, how to compress images and PDFs properly and which format to choose for your website.
Lossless vs lossy compression
Lossless compression makes a file smaller while keeping it identical when opened. You could compare the two pixel by pixel and find no difference. It works because many files are stored inefficiently in the first place. PNG, SVG, GIF and Office files can all be compressed this way.
Lossy compression trades some quality for a much smaller file. JPG works like this. Re-saving a JPG always creates a fresh version, but at high quality settings the difference is invisible to almost anyone, and the file is usually much smaller.
Plenty of tools call everything “lossless”. Squish only uses the word where the file genuinely decodes to identical pixels.
What Squish can shrink
- PNG: rebuilt losslessly for an identical image in a smaller file, with an option to reduce colours for more savings.
- JPG: re-encoded more efficiently than most cameras manage, with hidden metadata stripped out.
- WebP and AVIF: modern formats that are usually far smaller than JPG.
- PDF: tidied losslessly, or rebuilt from images for scanned documents. Scan mode makes text non-selectable, so Squish warns you first.
- SVG and GIF: cleaned up and optimised, with animations kept intact.
- Word, Excel and PowerPoint: repacked more tightly, with preview thumbnails dropped.
- Audio: WAV files converted to MP3 at a bitrate you choose.
Everything runs inside your browser, so your files are never uploaded. That makes it safe for contracts, invoices and client work. Try Squish, our free file compressor.
Why did my PDF barely shrink?
Text-based PDFs are already stored efficiently, so lossless mode may only find small savings. The big wins come from scanned documents, which are really a stack of photos. For those, scan mode can make a dramatic difference.
Which image format for your website?
- AVIF for the smallest files, if you only need modern browsers.
- WebP as the safe middle ground, with very wide support.
- JPG if it has to work absolutely everywhere.
- PNG in lossless mode for logos and flat graphics, or SVG for logos where possible. See logo files explained.
Compression is only half of it. Resize photos to the width they will actually be displayed at before compressing. A photo straight off a phone is usually far bigger than any website needs. Faster pages help visitors and search results. See why your website feels slow.
A simple routine
- Resize photos to the size you need.
- Choose the right format for the job.
- Compress, then check the result looks right.
- Keep your originals in a safe place, and upload the smaller copies.
If you need to change formats first, such as HEIC photos from an iPhone, see converting files without uploading them.
Want a website that stays fast?
Madexify builds and maintains fast websites for small businesses across Pakenham, Officer, Beaconsfield, Berwick, Narre Warren, Cranbourne, Clyde and Bunyip, with images optimised as part of the job. See our web design and development services, or contact us to talk about your website.
This article is part of our Small Business Website Guide. Browse all our guides on the guides page.
