TL;DR: To compress images without losing quality, first resize the image to the size it will actually be shown at, then save photos as WebP at quality 75 to 85. That combination shrinks most photos by 60 to 90 percent with no difference your eyes can see. Keep a copy of the original, because lossy compression cannot be undone.
Last checked: 13 October 2026. Format figures and speed thresholds below were checked against Google’s developer documentation and MDN on this date.
One honesty note before the steps. Strictly, compression is either lossless, where every pixel survives and savings are modest, or lossy, where data is discarded and savings are huge. When people say “without losing quality” they mean the second kind done well: loss you cannot see. Most guides blur that distinction, and one top result even promises true losslessness for web photos. This guide keeps the two apart, so you always know what you are trading.
Can you really compress images without any quality loss?
Yes, but only with lossless compression, and the savings are smaller. Lossless methods, PNG and lossless WebP, shrink a file without discarding a single pixel, typically saving 10 to 30 percent on photographs. Lossy methods, JPEG, standard WebP and AVIF, discard detail your eyes barely register and routinely save 60 to 90 percent. Both are legitimate; they answer different needs.
Choose by content, not habit. Keep logos, screenshots with text, diagrams and anything headed for print or further editing in a lossless format or as an untouched master. Publish photographs and general web images in a lossy format at sensible quality settings, where the discarded data is detail nobody can see at normal viewing sizes. The rest of this guide is about doing the lossy kind properly, because that is where the real savings, and the real mistakes, live.
Which format should you use: JPEG, WebP or AVIF?
For most web images in 2026, WebP is the practical default. Google’s own figures state that lossy WebP images are 25 to 34 percent smaller than comparable JPEGs at the same quality, and lossless WebP is 26 percent smaller than PNG. AVIF goes further: MDN puts lossy AVIF at around 50 percent smaller than JPEG. JPEG remains the fallback every device on earth can open.
| Format | Saving versus JPEG | Browser support | Best for |
|---|---|---|---|
| WebP | 25 to 34 percent smaller (Google) | All modern browsers; Safari since version 14 | The default choice for web photos |
| AVIF | Around 50 percent smaller (MDN) | Chrome, Firefox, Edge; Safari in full from 16.4 | Smallest files where a fallback exists |
| JPEG | Baseline | Universal, every device and app | Email, documents, maximum compatibility |
| PNG | Lossless; larger than JPEG for photos | Universal | Logos, text, transparency, masters |
Ignore any guide that still warns you Safari cannot open WebP: Apple added support in Safari 14, years ago. The sensible setup is WebP for everything, AVIF where your tools serve it with a WebP or JPEG fallback, and PNG only where pixels must survive untouched. Saving a photograph as PNG “for quality” is the classic error: the file can be five times heavier with zero visible benefit.
What quality setting should you use for photos?
Between 75 and 85 for JPEG and WebP photographs. That is a working range, not an official table: quality scales are subjective and differ between tools, which is why Google publishes no universal number. The range is still well anchored. Google’s Lighthouse audit re-encodes JPEGs at quality 85 when judging whether your images are optimised, and WordPress’s own WebP guidance uses 75 as its example value.
At quality 80, a typical photo loses half to two thirds of its weight with no visible change at normal sizes. Below about 60, blocky patches appear in skies and gradients, and faces start to smudge. Screenshots and images containing text play by different rules: keep them PNG, or use quality 90 or higher, because crisp edges are exactly what lossy compression sacrifices first. Whatever you choose, judge at 100 percent zoom on the busiest part of the image, not on a thumbnail.
How do you compress an image step by step?
Use a tool that works on the file directly, such as our free image compressor, which runs entirely in your browser so your images are never uploaded to a server. Work on a copy, keep the original archived, and follow the order below, because the sequence matters more than any single setting: resize first, format second, quality last.
- Resize to the display size. A photo shown at 800 pixels wide gains nothing from being 4,000 pixels wide. Cutting 4,000 down to 1,200 pixels alone can remove about 80 percent of the weight before compression even starts.
- Choose the format. WebP for photos on the web, AVIF if offered with a fallback, JPEG for email and documents, PNG for graphics and text.
- Set quality between 75 and 85. Start at 80. Raise it only if the comparison in the next step shows damage.
- Compare before and after at full size. Zoom into faces, text and gradients. If you cannot tell which file is which at normal viewing distance, the setting is right.
- Save under a clear new name. Something like harbour-sunset-web.webp keeps the compressed copy obvious and your original safe.
A worked example shows what to expect. A 6 MB phone photo resized to 1,600 pixels on its long edge and saved as WebP or JPEG at quality 80 typically lands between 300 and 600 KB: roughly a 90 percent reduction that looks identical on a screen. Heavy originals are also why phones fill up, so the same workflow pairs well with our guide to speeding up a slow Android phone.
How can you reduce an image below 100 KB for a form?
Resize the dimensions before you touch the quality slider. Upload forms for passports, job applications and exam entries usually reject files over a set size, and crushing quality to hit it produces a large, mushy picture. A smaller, sharper image always wins: reduce the long edge to 1,200 pixels or less, save as WebP or JPEG, then lower quality gradually from 80 until you slip under the limit.
Worked example: a 4 MB scan saved at 1,600 pixels and quality 80 might land near 400 KB. The same scan at 1,000 pixels and quality 75 usually drops under 100 KB while the text stays perfectly readable, because documents are mostly flat colour. If a form demands a specific format, usually JPEG, convert last and re-check the size, since JPEG at the same settings weighs more than WebP. And if the image carries a mark or logo you need gone first, clean it with the watermark remover before compressing, never after.
What image speeds does Google actually measure?
Three Core Web Vitals thresholds, checked at the 75th percentile of real visits: Largest Contentful Paint at 2.5 seconds or less, Interaction to Next Paint at 200 milliseconds or less, and Cumulative Layout Shift at 0.1 or less, per Google’s web.dev documentation. Images are usually the Largest Contentful Paint element, so their weight is the single biggest lever most sites have.
Two details rival guides keep getting wrong. First, Interaction to Next Paint replaced First Input Delay as a Core Web Vital on 12 March 2024, as Google announced at the time; any checklist still grading you on FID is two years out of date. Second, never lazy load your main hero image: lazy loading delays the very picture Google is timing. Set explicit width and height on every image too, so the page does not jump as pictures arrive, and size social images with our Instagram Reels resizer when the destination is a feed.
What should WordPress users do differently?
Less than plugin adverts suggest, because WordPress handles more natively than it used to. WebP uploads have worked without any plugin since WordPress 5.8 added WebP support in 2021. WordPress also adds lazy loading to images by default, and when it generates resized copies of your uploads it encodes JPEGs at quality 82. None of that requires an optimisation plugin, an account or an API key.
Your one real job is to compress before you upload. WordPress stores your original file untouched and builds its smaller sizes from it, so uploading a 6 MB photo means storing a 6 MB photo forever, even if visitors only ever see a resized version. Shrink the file first using the workflow above, then upload. Plugins still earn their place for one task: bulk-converting a large old media library you cannot redo by hand, and even then, back up before you let anything rewrite hundreds of files.
Frequently asked questions
Does reducing image size reduce quality?
It depends which size you mean. Reducing dimensions throws away pixels, which is fine when the image was larger than its display size anyway. Reducing file size through lossy compression discards fine detail, invisibly at quality 75 to 85 for photos. Reducing either from an already small file, or re-saving a JPEG repeatedly, is where visible damage creeps in.
Does compressing images affect SEO?
Yes, positively, when done properly. Faster pages help your Largest Contentful Paint score, one of the Core Web Vitals Google measures at 2.5 seconds or under, and visitors on slow connections stop abandoning heavy pages. Compression only hurts when it goes too far: blurry product photos and unreadable text damage trust and conversions far more than a few extra kilobytes ever would.
Is online image compression safe?
It depends where the processing happens. Server-based tools receive a copy of your image, which matters for private documents, ID scans and unreleased product shots. Browser-based tools such as the Savozi compressor process the file on your own device, so nothing leaves your machine. Check which kind a tool is before uploading anything sensitive; the honest ones say so plainly.
Can I compress hundreds of images at once?
Yes. For a website backlog, a WordPress optimisation plugin can process the whole media library in bulk, though free tiers are capped and the good ones need an account. For a folder of photos on your computer, batch tools and most browser compressors accept multiple files at once. Either way, back up the originals first, because bulk lossy compression cannot be undone.
What is the ideal image size for a website?
There is no single number, but working targets serve most pages well: hero images under 200 KB, ordinary content images between 50 and 150 KB, and thumbnails under 30 KB, each resized to no more than twice its display width for sharp screens. Hit those with WebP at quality 80 and your pages will feel fast on ordinary mobile connections.
The whole method in one line: resize first, choose WebP, set quality near 80, and keep the original. Every Savozi utility mentioned here is free, and the rest live on the free tools hub.
