To compress an image without visible quality loss:

1. Resize it to the dimensions you actually need. 2. Convert JPG and PNG photos to WebP (or AVIF). 3. Use quality 75 to 85 for JPEG and WebP. 4. Remove unnecessary metadata. 5. Compare the result at 100 percent zoom.

In most cases this cuts file size by 50 to 80 percent while staying visually identical to the original. If you just want it done now, use our JPG compressor or PNG compressor, or convert a photo with JPG to WebP. The rest of this guide explains why each step works, so you can make the right call for your own images.

Almost every compression tool promises smaller files “without losing quality.” That phrase is doing a lot of quiet work, and being honest about it is the difference between a tool you can trust and marketing.

There are two kinds of “no quality loss”:

Mathematically lossless means the decompressed pixels are bit-for-bit identical to the original. Nothing is thrown away. PNG, WebP lossless, and lossless JPEG XL work this way. This is what you need for medical images, technical diagrams, pixel art, and master archives.

Visually lossless means the pixels do change, but a human cannot see the difference at normal viewing size. This is the regime where JPEG quality 85, WebP quality 80, and AVIF quality 50 live. The file is not identical to the source, but on a normal screen at a normal distance you will never tell.

When people say “compress without losing quality,” they almost always mean visually lossless. That is good news, because visually lossless is where the real savings are. True mathematically lossless compression only trims a JPEG by about 2 to 10 percent. Everything beyond that comes from changes your eyes were never going to notice.

Image compression is not magic and it is not lying to you. It exploits a real, measurable limitation of human vision: we see fine detail in brightness far better than we see fine detail in color.

Formats like JPEG, WebP, and AVIF first split an image into one brightness channel (luma) and two color channels (chroma). Because the eye is roughly three times less sensitive to spatial detail in color than in brightness, the encoder can store the color channels at half resolution with almost no visible difference. This trick is called chroma subsampling, and the common 4:2:0 mode throws away three quarters of the color samples while keeping every brightness sample. You do not notice because your eyes were never going to resolve that color detail anyway.

On top of that, JPEG breaks the image into small blocks and gently rounds off the high-frequency detail in each one. The quality slider is simply how aggressively it rounds. At quality 85 the rounding is invisible on a photo. At quality 40 you start to see blocky edges and halos around sharp lines. Understanding this is the whole game: good compression spends its budget where your eyes look and saves bytes where they do not.

For photographs, JPEG is still the safe, universal choice. Here is how to make it small without a visible penalty.

Use quality 75 to 85. This is the sweet spot for photos. Above 95 the file grows fast for a difference no one can see. Below 70 you start to get visible blocking. For most web photos, quality 80 to 82 is indistinguishable from the original.

Re-encode with mozjpeg, not the default encoder. mozjpeg is a tuned JPEG encoder that produces files about 5 to 15 percent smaller than a standard encoder at the same visible quality, using smarter quantization and entropy coding. The only cost is encode speed, which is irrelevant for a one-time conversion. Convertify uses mozjpeg-grade settings under the hood.

Let chroma subsampling do its job. A good encoder picks subsampling based on quality: around quality 90 and above it keeps full color resolution (4:4:4), and below that it subsamples color (4:2:2 or 4:2:0). For ordinary photos 4:2:0 is the right default. Force full color only for screenshots of colored text or hard graphic edges, where chroma subsampling can cause faint fringing.

Never re-save a JPEG over and over. Every time you open a JPEG and save it again as JPEG, the encoder re-rounds data that was already rounded, and the damage stacks. This is called generation loss. Keep a lossless source (PNG, TIFF, or the camera original) and export the JPEG from that source in one step.

When you just need a smaller JPEG, our JPEG compressor applies these settings for you. If the image is headed for the web, converting it with our JPG to WebP converter usually beats compressing the JPEG.

PNG is where the word “lossless” causes the most confusion, because there are two completely different ways to shrink a PNG.

Lossless PNG optimization (truly no quality loss). Tools like oxipng and zopflipng re-run the internal filtering and compression with a smarter search and strip junk metadata, without touching a single pixel. The output is mathematically identical to the input. Savings are typically 20 to 60 percent on raw screenshots and 5 to 15 percent on files that were already exported tightly. Use this for anything where a single changed pixel would matter.

Palette quantization (visually lossless for the right images). Tools like pngquant rebuild the image using a smaller color palette, often 256 colors. For logos, icons, UI elements, and flat illustrations that never had many colors to begin with, this is visually identical and routinely cuts around 70 percent of the file size. For smooth gradients and photographs it can cause visible banding, so it is the wrong tool there.

The honest catch: PNG is the wrong format for photos. PNG was built for sharp graphics with flat color, not for photographic detail. If you compress a photo as PNG you get a huge file for no benefit. Our own benchmarks below show a JPEG photo converted to PNG growing by 78 percent, and an AVIF photo to PNG growing nearly fourfold. For a photo with transparency that needs to go on the web, WebP or AVIF with an alpha channel is far smaller than PNG at the same quality.

To shrink a PNG safely, use our PNG compressor. If the PNG is actually a photo, convert it with PNG to WebP instead.

For web images, the single biggest win is usually not tweaking JPEG or PNG settings. It is switching format.

WebP is 25 to 34 percent smaller than JPEG at the same measured quality, and its lossless mode is about 26 percent smaller than PNG, according to Google's own reference study. It supports transparency and is supported by every modern browser, which makes it the safe default for the web.

AVIF goes further, roughly 50 percent smaller than JPEG at matched quality, with support for 10-bit color and HDR. Netflix published exactly this result when it adopted AVIF. The trade-off is slower encoding, which only matters at scale, not for a single file.

One honest caveat most articles skip: Google's 25 to 34 percent figure compares WebP against the standard JPEG encoder. Once you compare against a tuned mozjpeg, the gap narrows a lot, and for some image sizes a well-encoded JPEG can match or beat WebP. WebP and AVIF are still the right call for the web in 2026, but the headline numbers assume a weaker JPEG baseline than you would actually use. JPEG XL is technically excellent but is still behind a flag in most browsers in 2026, so treat it as an archival format for now, not a delivery one.

If you want the full format breakdown, see our deep dive on AVIF vs WebP vs HEIC. To convert now, use JPG to WebP, PNG to WebP, or HEIC to WebP, or shrink an existing WebP with our WebP compressor.

These are real measurements from 24 iPhone photos run through our own libvips pipeline in June 2026, not numbers from a spec sheet. They are conversions rather than same-format compression, but they make the most important point in this whole guide clear: format choice moves file size more than any quality slider.

Moving photos into WebP cut size dramatically every time, up to 90 percent from PNG and 55 percent from JPG. Moving photos into PNG made them larger every time, because PNG keeps every pixel exactly and a photo has no flat areas to save on. HEIC to JPG even grew the file by 15 percent, because HEIC is already an efficient modern codec and plain JPEG is not, so re-encoding to JPEG spends more bytes for the same picture.

The lesson is simple. If your goal is the smallest file at the same visible quality for the web, convert to WebP or AVIF first, and only then think about quality settings. Picking the right format is the lever that pays off the most.

Before you touch a quality slider, ask one question: how big will this image actually be displayed? A photo straight off a phone can be 4000 pixels wide. If it will be shown in a 600-pixel-wide column, you are sending more than forty times the pixels anyone will see.

Resizing to the real display size is by far the largest saving available, and it costs you nothing visible, because the extra pixels were never going to be seen. A 4000-pixel photo resized to 1600 pixels wide is already many times smaller before any compression happens, and it will look identical in its slot on the page.

The right order is: resize to the displayed dimensions first, then strip metadata, then compress. A correctly sized image at quality 85 almost always beats a full-size image at quality 50, on both file size and sharpness. Use our image resizer to set exact dimensions, or our image cropper when you also need a specific shape or aspect ratio.

Any of the tools above will compress images well, so the choice comes down to your setup and how much control you want.

If you want something instant with nothing to install, a browser tool is the simplest path. Convertify runs entirely online, has no signup and no watermark, and handles both compression and format conversion in one place, which matters because for the web the right move is often converting to WebP rather than compressing the original. Squoosh is excellent when you want to tweak codec settings by hand and watch the file size change live. TinyPNG is a quick option focused on palette compression for PNG and JPG.

If you prefer a desktop app for batch work, ImageOptim is the long-standing lossless optimizer on Mac, and Caesium covers batch compression on Windows. For automated build pipelines, command-line tools like mozjpeg, oxipng, and pngquant are the standard, since they slot into a deploy step and run without a UI.

For most people the honest answer is: resize first, then use whichever tool is already in front of you. The format and the dimensions matter far more than which specific compressor you pick. You can start right now with our JPG, PNG, and WebP compressors.

Compression is not just about saving disk space. On the web it directly affects how fast your page feels and how Google scores it.

Google's Largest Contentful Paint (LCP) measures how long it takes for the biggest element in view to render, and on most pages that element is an image. The target is under 2.5 seconds for most of your real visitors. The image's download time is a direct part of that number, so cutting a hero image from 500 KB to 160 KB can be the difference between passing and failing on a slow mobile connection.

A few practical rules: never lazy-load the main hero image, serve different sizes for different screens, and offer AVIF or WebP with a JPEG fallback so each browser gets the smallest format it understands. Smaller images are not a nice-to-have; they are one of the highest-leverage things you can do for page speed and ranking.

Put it all together and compression stops being guesswork:

1. Resize the image to the size it will actually be displayed at. This is the biggest saving. 2. Strip metadata, but keep the color profile if the image uses wide-gamut color, so the colors do not shift. 3. Pick the format for the job: WebP or AVIF for web photos, mozjpeg-grade JPEG when you must keep .jpg, lossless PNG or palette PNG for graphics and logos. 4. Set a perceptual quality (JPEG 80 to 85, WebP 75 to 80, AVIF 45 to 55) instead of chasing 100. 5. Check the result on a real screen at real size before shipping.

All of these tools are free and run instantly: compress JPG, compress PNG, compress WebP, resize image, and converters like JPG to WebP and PNG to WebP. No signup, no watermark, and your files are processed without being kept.