Lossy vs Lossless Image Compression: Which Should You Use?

Every time you save an image, you make a choice: keep every pixel exactly as-is, or let the encoder discard some data to make the file smaller. That choice — lossy vs lossless compression — determines file size, quality, and which formats you should reach for. This guide explains both approaches clearly so you can make the right call every time.

What is lossy compression?

Lossy compression permanently removes image data to achieve smaller file sizes. Once the data is gone, it cannot be recovered — saving a JPEG discards information that no future software can restore.

The encoder exploits limitations of human vision: the eye is less sensitive to fine color detail than to luminance (brightness), so color information is aggressively reduced. The result is a file that looks very similar to the original but takes a fraction of the space.

Common artifacts introduced by lossy compression include:

• 8×8 pixel blocking — JPEG divides images into 8×8 blocks; at low quality settings these blocks become visible as a grid pattern
• Color banding — smooth gradients (sky, skin tones) show discrete steps instead of a continuous blend
• Edge ringing — dark halos or ghosting around high-contrast edges like text on a white background

Typical size reduction: 70–90% smaller than the uncompressed original.

Formats that use lossy compression by default:

• JPEG / JPG
• WebP (default mode)
• AVIF (default mode)
• HEIC

What is lossless compression?

Lossless compression reduces file size without discarding any image data. The decompressed image is pixel-identical to the original — every red, green, and blue value is preserved exactly.

Instead of throwing data away, lossless encoders find patterns and redundancy in the pixel data and represent them more efficiently. A run of 500 identical white pixels can be encoded as "500× white" instead of storing each individually.

Typical size reduction: 20–50% smaller than uncompressed, which is far less dramatic than lossy — but quality is guaranteed.

Formats that support lossless compression:

• PNG (always lossless)
• GIF (always lossless, limited to 256 colors)
• WebP (lossless mode — must be explicitly selected)
• AVIF (lossless mode — must be explicitly selected)
• TIFF (with LZW or ZIP compression)
• BMP (typically uncompressed — no compression at all)

Side-by-side comparison

When to use lossy compression

Lossy compression is the right choice whenever slight quality loss is invisible or irrelevant:

• Photographs (portraits, landscapes, product shots) — the human eye tolerates small quality differences in natural images with complex color variation
• Web images where page speed matters — a 150 KB JPEG loads 10× faster than a 1.5 MB PNG of the same photo
• Social media uploads — platforms re-compress your images anyway, so uploading lossless PNG provides no benefit and wastes bandwidth
• Any image where exact pixel accuracy doesn't matter — background textures, hero banners, blog photos

When to use lossless compression

Lossless compression is essential when quality must be preserved exactly:

• Logos, icons, and text-heavy graphics — sharp edges and solid colors make JPEG artifacts immediately visible; a lossy logo looks unprofessional
• Screenshots — fine text rendered at 1× or 2× resolution blurs with lossy compression, making documentation unreadable
• Diagrams, charts, and infographics — compression artifacts make data labels and axis values hard to read
• Archiving source files — keep originals lossless; export lossy copies for delivery
• Images you will edit again — resaving a JPEG degrades it further each time (generation loss); use PNG for working files

How to choose in practice

• Photo for a website? → JPEG at quality 80, or WebP at quality 80–85 (lossy)
• Logo for an email signature? → PNG (lossless)
• Screenshot in documentation? → PNG (lossless)
• Profile photo for social media? → JPEG at quality 85 or WebP is fine (lossy)
• App icon? → PNG or SVG (lossless/vector)
• Animated image? → WebP (lossy) or GIF (lossless, 256 colors only)

Compression quality settings explained

For lossy formats, a quality slider controls the trade-off between file size and visual fidelity:

• Quality 85–90 — excellent results; artifacts are barely perceptible even on close inspection
• Quality 70–85 — good for web; differences are noticeable only when comparing side by side at 100% zoom
• Quality 60–70 — acceptable for thumbnails and previews
• Below 60 — visible artifacts; avoid for any important image

For most web images, quality 80 is the sweet spot: files are small enough to load quickly and quality is high enough that viewers won't notice the compression.

Try it yourself

Not sure which setting is right for your image? Picovert's image compressor lets you compress photos with adjustable quality and preview the result before downloading. To change formats entirely — for example converting a JPEG to lossless PNG — use the image converter.