Large images are the single most common cause of slow web pages. A photograph straight off a smartphone can be 5–8 MB. The same image, properly sized and compressed, can come in under 200 KB with no visible difference on screen. Here's how to do it.
Understand what "compression" actually means
There are two kinds. Lossy compression (JPG, WebP) discards image data that the human eye won't miss — mostly subtle colour gradients and high-frequency detail. Lossless compression (PNG with optimization) reorganises the file structure to encode the same pixels in fewer bytes. For photographs, lossy wins on size; for logos and screenshots with flat colours, lossless is better.
The dimension problem
Before touching quality settings, check the image dimensions. A 4000 × 3000 pixel photo displayed at 800 × 600 on a webpage is sending four times more pixels than the browser will ever show. Resize to your display width first. On a standard desktop layout that's usually 1200–1600 px wide at most.
Quality settings: what the numbers mean
In most tools, quality is expressed as a percentage. Research consistently shows that quality settings between 75 and 85% are indistinguishable from 100% to the human eye for most photographic content. Going below 70% starts to produce visible artefacts — blocky areas, colour banding — especially in skies and smooth gradients.
A practical workflow: start at 80%, check the output, drop to 70% if the file is still too big. Rarely go below 65%.
JPG vs WebP vs PNG — which to use
JPG is the safe default for photographs. Every device, browser and application supports it.
WebP produces files 25–35% smaller than JPG at the same visual quality. All modern browsers (Chrome, Firefox, Safari 14+, Edge) support it. Use WebP for web publishing; use JPG when the file needs to open in older software or be attached to an email to someone using Outlook.
PNG is best for images with transparent backgrounds, screenshots, and graphics with flat colours and sharp edges. For photographs, PNG files are usually much larger than JPG with no visual benefit.
A quick test you can do right now
Drop one of your images into the image compressor, set quality to 80% and max dimension to 1920, and compare the size before and after. Most people find the reduction is between 50% and 80% with no visible quality loss. If the result still looks good at 70%, you have even more room to compress.
Batch processing
The compressor accepts multiple files at once. For a folder of images, drag them all in and download them together. Each file is processed independently with the same settings, so resizing one very large image won't affect the others.
One last thing: the format of the upload portal
Many government portals and job application systems cap uploads at 200 KB or 500 KB. If you're preparing a document scan, use the image to PDF tool to combine pages, then compress the source images first to keep the PDF under any size limit.