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Dev.to
7/29/2026
Compressing an image to exactly 50KB in the browser, with no server

Compressing an image to exactly 50KB in the browser, with no server

Short summary

A practical guide to compressing images to an exact byte target (e.g., 50KB) entirely in the browser using canvas.toBlob and binary search over JPEG quality. The author honestly documents limitations: no resolution-scaling fallback, main-thread blocking, EXIF orientation issues, and PNG's quality parameter being a no-op. India context: motivation came from government exam portals requiring sub-50KB uploads.

  • •Binary search over JPEG quality (8 iterations) reliably hits byte targets in-browser
  • •Author transparently documents unresolved edge cases: large-image floor, EXIF rotation, main-thread blocking
  • •Motivated by Indian government exam portals requiring sub-50KB photo uploads

Generated with AI, which can make mistakes.

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