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change-jpg-quality

JPG (JPEG) is a lossy format with a quality slider — 100 is near-original, 1 is heavily compressed. Most cameras shoot at 90-100, which is bigger than needed for web. Re-saving at quality 75-85 typically halves the file with no perceptible loss. The ZTools Change JPG Quality tool decodes the JPG, re-encodes via the browser's native JPEG encoder at your chosen quality, and shows before/after side by side so you can pick the smallest acceptable level.

Use cases​

Compress photos for the web​

A 4 MB camera JPG is too big for a hero image. Re-save at quality 80 → ~600 KB; quality 70 → ~400 KB. Loss is negligible at typical screen sizes.

Email attachment under quota​

A 25 MB email limit; original photos exceed it. Quality slider lets you fit under the limit without external services.

Reduce screenshot bloat​

iPhone screenshots default to PNG (large). Re-save as JPG quality 85 — 5x smaller, visually identical.

Iterate on quality vs size​

Side-by-side preview makes the tradeoff visible. Pick the lowest quality where the artefacts are still acceptable.

How it works​

  1. Pick JPG file — Drag-drop or select. Decoded into a canvas.
  2. Move quality slider — 1 (extreme compression) to 100 (max retention). Default 80.
  3. Preview — Original and re-encoded side by side. Tool shows new file size in KB.
  4. Download — One-click save as new .jpg. Original file untouched.

Examples​

Input: 4000×3000 photo at quality 95, 4.2 MB

Output: Quality 80: 1.1 MB. Quality 70: 720 KB. Quality 50: 380 KB (some artefacts visible).

Input: Same photo at quality 90 (default many cameras)

Output: Most users can't spot the difference between 90 and 80; difference between 80 and 60 is noticeable on flat colour areas.

Frequently asked questions​

How low should I go?

85 for editorial photography, 75-80 for general web use, 60-70 for thumbnails. Below 50, blocking artefacts become visible especially in skies and skin.

Is the loss cumulative?

Yes — every re-save loses more. Always work from the highest-quality source you have. Going from 95 → 80 → 65 is worse than going directly from 95 → 65.

Why is JPG always lossy?

JPEG's discrete cosine transform discards high-frequency information. Even quality 100 isn't pixel-identical to the original. For lossless, use PNG or WebP lossless.

Does the EXIF survive?

Browser-native canvas encoders typically strip EXIF on re-encode. Toggle "preserve EXIF" if you need camera metadata kept.

Privacy?

All compression in the browser. Photos never uploaded.

Tips​

  • Quality 80-85 is the universal sweet spot. Going higher rarely helps; going lower starts showing artefacts.
  • For images with text or sharp edges, prefer PNG or WebP lossless — JPG smears edges.
  • Re-save once from your master — don't compound losses by saving at 70 then dropping to 50.
  • Before publishing, view at 100% zoom on a large monitor — artefacts that hide on a phone show up on desktop.

Try it now​

The full change-jpg-quality runs in your browser at https://ztools.zaions.com/change-jpg-quality — no signup, no upload, no data leaves your device.

Open the tool ↗

Last updated: 2026-05-06 · Author: Ahsan Mahmood · Edit this page on GitHub