Image Compression
Compress an Image Without Losing Quality
The honest answer: true lossless compression only goes so far. But there's a quality range where the difference is invisible to the human eye — and that's close enough for almost every use case. Here's how it works.
What "no quality loss" actually means
When people say they want to compress an image without losing quality, they usually mean: compress it so I can't tell the difference. That's achievable. JPEG at 80–90% quality looks identical to the original in almost every real-world context — on screens, in emails, on websites.
Technically, there's data loss happening. But the data that's discarded is the fine colour variation in smooth gradients that the human visual system processes poorly anyway. The result: a file 50–80% smaller that looks the same.
Quality settings: what to use when
PNG: genuinely lossless options
PNG uses lossless compression, so you can reduce a PNG file size without any quality change — but the savings are limited, typically 5–20%. PNG optimisers like TinyPNG use a technique called quantization that reduces the number of colours in the image before compressing. For logos and flat graphics this can cut file sizes by 50–70% with no visible change.
For photographs saved as PNG, the best approach is to convert to JPEG at 80–85% quality. A 5 MB photo PNG might become a 400 KB JPEG that looks identical on screen.
The one rule: always compress a copy
Once you save a JPEG at lower quality, that quality loss is baked in permanently. If you then compress it again, you're applying quality loss on top of quality loss. Always keep the original file and compress a copy — the original is your safety net.
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Use it →Frequently asked questions
Can you compress a JPEG without any quality loss?
Not really. JPEG is inherently lossy — every time you save a JPEG with quality settings, some data is discarded. What you can do is compress at a high quality setting (85–90%) where the loss is visually undetectable to most people. Mathematically the image changes; visually, most viewers can't tell. That's the practical definition of 'no quality loss' for JPEG.
What compression setting gives the best quality-to-size ratio?
For most photos, 75–85% quality is the sweet spot. The file is typically 60–75% smaller than the uncompressed version, and the quality loss is invisible to the naked eye unless you're viewing at 100% zoom and comparing side by side. Below 60%, compression artefacts (blocking, blurring around edges) start to become visible.
Is PNG compression lossless?
Yes. PNG uses lossless compression — every pixel is preserved exactly. However, PNG files are much larger than JPEG for photographs. If you compress a PNG file, you can reduce its size somewhat by optimising the compression algorithm, but you cannot apply JPEG-style quality reduction to a PNG and keep it as PNG. The main way to dramatically reduce a PNG file size is to convert it to JPEG.
What is the difference between lossy and lossless compression?
Lossless compression reduces file size without discarding any image data — the original can be perfectly reconstructed. PNG and GIF use lossless compression. Lossy compression achieves much smaller file sizes by permanently removing image data that the human visual system is least likely to notice. JPEG uses lossy compression. WebP supports both lossy and lossless modes.
Does compressing an image reduce its resolution or dimensions?
Not automatically. Quality-based compression (like adjusting JPEG quality) keeps the image dimensions exactly the same — it reduces file size by encoding the existing pixels more aggressively. If you want to reduce dimensions (width × height), that's resizing, not compression. Both can be done independently.
Can you restore quality after compressing an image?
No. Once image data is discarded through lossy compression, it cannot be recovered. Applying an AI upscaler or sharpening filter can make the image look slightly better to the human eye, but the original pixel data is gone. This is why it's important to keep an original copy before compressing — always compress a copy, not the original.