Optimize Images for Websites
Heavier images are usually the main reason for slow websites. Use our optimizer to make your assets as lean as possible, helping both your SEO and your user experience.
Last updated: August 2026
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Supports JPG, PNG, WebP and AVIF
Image optimisation is usually presented as a compression problem, and it mostly is not. Three decisions come before any quality slider: how large the image needs to be in pixels, which format it should be in, and how much total weight the page is allowed. Get those right and compression becomes a small adjustment at the end. Get them wrong and no compression setting rescues the page — you are just choosing how bad a too-large image in the wrong format will look.
Dimensions come first because they are pure waste. An image displayed at 800 pixels wide but served at 3000 costs roughly fourteen times the pixels for no visible benefit, and every visitor pays for it. Format comes second because it is the only lever that buys size without costing quality: the same photograph as WebP or AVIF is meaningfully smaller than as JPEG at the same visible fidelity. Compression comes third, and by then it is fine-tuning.
The last decision is the one most sites never make explicitly: a weight budget for the page as a whole. Judging each image in isolation is how a page ends up with fifteen individually reasonable images and an unreasonable total. Decide what the page may weigh, divide it across the images you are actually shipping, and the per-image targets fall out of that arithmetic instead of being guessed at one file at a time.
How to optimize images for a website
- 1
Size to the display width
Measure how wide each image is actually drawn, then serve roughly twice that to cover high-density screens. Resize Image does the work; anything beyond that is downloaded and discarded.
- 2
Choose the format deliberately
WebP for most web photography, AVIF where you can arrange a fallback, PNG only for graphics that need lossless edges. Convert JPG to WebP covers the common move.
- 3
Set a per-image budget from the page budget
Decide the page total first, then divide. A lone hero can take a few hundred kilobytes; a gallery of twenty cannot.
- 4
Compress to that target
Add the images here, set the target, and let quality be chosen automatically. At sensible dimensions the required quality is usually high enough to be invisible.
Pro tip: Optimise the largest image on the page first and stop when the numbers stop moving. Page weight is almost always dominated by two or three files — usually a hero image and whatever the biggest in-article photo is — while a long tail of small assets contributes very little. Working through every image on a site in order is slow and mostly wasted; sorting by file size and fixing the top of that list gets you most of the benefit in a fraction of the time.
Troubleshooting: If pages are still slow after compressing everything, check dimensions rather than compression — an image served far larger than it is displayed is the most common remaining cause. If images look soft on phones, they were sized to their display width rather than twice it. If the total weight is high despite every individual image being reasonable, that is the page-budget problem: too many images rather than any one being too large.
For the strategy behind these decisions, How to Optimize Images for Core Web Vitals goes deeper, and Best Image CDNs for Faster Websites covers automating it. For processing many files at once, Bulk Image Compressor. Format-specific work lives in Optimize PNG for Faster Loading and Convert Image to AVIF, and article images in Resize Image for Blog Post.
Frequently asked questions
How do I optimize images for a website?
In three steps, in order: resize to roughly twice the display width, convert to a modern format such as WebP, then compress to a target derived from your page weight budget. Compression alone, without the first two steps, produces far worse results for the same file size.
What is the best image format for websites?
WebP for most photographic content — every current browser supports it and it is meaningfully smaller than JPEG at the same visible quality. AVIF is smaller still where you can arrange a fallback. PNG only for graphics that genuinely need lossless edges, since it is a poor fit for photographs.
How much should a web image weigh?
It depends on how many arrive with it. Divide a page weight budget across the images you are actually shipping rather than judging each one alone — a single hero image can justify a few hundred kilobytes where each of twenty gallery images clearly cannot.
Does image optimization help SEO?
Indirectly, through loading performance. Search engines measure how quickly a page becomes usable, and images are usually the largest thing standing between a visitor and that moment. The ranking benefit comes through speed rather than from the images themselves.
Are my images uploaded to a server?
No. Everything runs inside your browser on your own device, so a whole site's worth of assets can be processed without any of it being uploaded, stored, or logged.
Looking for the full-featured version? Open the main Compress Image tool.
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