Free tool · runs in your browser

Thumbnail Format Converter

Convert a thumbnail or any image between JPG, PNG, and WebP, choose a quality level for the lossy formats, and see the before/after file size instantly. Everything runs in your browser — nothing is uploaded.

How to use this tool

  1. 01

    Upload your image

    Any common format works — it's converted in your browser and never uploaded.

  2. 02

    Pick output format

    WebP for the web, JPG for maximum compatibility, PNG for graphics or transparency.

  3. 03

    Pick quality (if applicable)

    High covers most cases; Max is for archival; PNG ignores quality since it's lossless.

  4. 04

    Convert and check file size

    Compare the before/after size — smaller is better as long as quality stays acceptable.

Why this matters

Creators end up with thumbnails in whatever format their editor exported, then hit a wall: a host wants JPG, a CMS demands WebP for page speed, a partner needs a transparent PNG. Re-exporting from the original project file for each one is slow, and most online converters make you upload an image you'd rather keep private.

This converter re-encodes the image right in your browser with the quality control that actually matters and shows the before/after size so you can see the trade you're making. When the goal is the smallest file at a target format rather than a format change, reach for the Thumbnail Compressor instead.

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FAQ

JPG is best for photographs and anything with smooth tonal gradients — it compresses them tiny with no visible loss at high quality. PNG is for graphics with sharp edges, text, or transparency, since it's lossless and won't ring around hard lines. WebP does both jobs and is meaningfully smaller at the same perceived quality, so it's the default for the web when you don't need legacy compatibility.

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