AVIFify

WBMP

.wbmp

A 1-bit monochrome bitmap from 1999 built for WAP feature phones. Smartphones long ago dropped it in favour of PNG, SVG, and modern formats.

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WBMP packs one bit per pixel — pure black or white, no grey, no colour, no transparency — and was built so a 1999 feature phone could draw a picture over a 9.6 kbit/s link. It is the opposite of AVIF in almost every dimension, which makes it a precise yardstick for how far mobile imaging has travelled. This page traces WBMP's WAP-era origin, its 1-bit limits, why it died, and what a modern phone running AVIF does instead.

What WBMP was built for

WBMP carried simple monochrome graphics to WAP browsers on 2G feature phones. The WAP Forum defined it around 1999 inside the Wireless Application Protocol 1.x stack, alongside WML (the markup language WAP pages were written in). Three constraints shaped every design choice:

  • Screens were 1-bit. Phones like the Nokia 7110 and Ericsson R380 had monochrome LCDs, so colour data would have been wasted bytes.
  • Radios were slow. GSM data ran at ~9.6 kbit/s, so a logo had to be tiny to arrive before the user gave up.
  • CPUs were weak. Handsets could not afford a heavy decoder, so the format stayed close to raw bits.

The result was a deliberately minimal format: a short header, then packed pixels, sized for screens around 96x65 pixels.

How 1-bit imaging works

Each pixel in WBMP is a single bit: 0 for black, 1 for white. There is no palette, no alpha channel, and no grey — a photograph must be reduced to two tones by dithering or thresholding before it can be stored. Eight pixels pack into one byte, rows pad to a byte boundary, and a compact variable-length integer encodes the width and height. For more on lossless storage trade-offs, see Lossy vs Lossless Compression.

That simplicity is the whole point and the whole limit. A two-tone icon stores cleanly; anything with shading, skin tones, or gradients falls apart.

Why WBMP is obsolete

WBMP is dead because every constraint it solved disappeared, and WAP itself was retired. Four shifts ended it:

  • WAP collapsed. The 2007 smartphone era replaced WML decks with full HTML browsers; carriers decommissioned WAP gateways.
  • Screens went full colour. Modern phones render millions of colours at retina density, so 1-bit output looks broken.
  • Bandwidth multiplied. 4G and 5G deliver megabits to gigabits, erasing the byte-pinching that justified WBMP.
  • Browsers dropped it. No current browser renders image/vnd.wap.wbmp; only emulators and a few libraries like ImageMagick still touch it.

There is no 2026 scenario where shipping WBMP to a phone is correct. The honest replacements are PNG for crisp two-tone marks and AVIF for photographs.

How far mobile imaging has come

A modern phone shows a full-colour photo in fewer bytes than WBMP ever spent on two tones. AVIF reaches roughly 94% of global users in 2026, per caniuse, and is supported on iOS 16+, Android Chrome 85+, and Firefox 93+. Concretely:

  • WBMP gave a ~96x65 phone screen black-and-white line art in around 800 bytes.
  • AVIF gives a full-resolution phone screen a 10-bit colour photograph, often at a comparable or smaller byte budget, because the AV1 codec compresses real images far better than raw bits.
  • AVIF adds what WBMP could never express: colour, alpha transparency, HDR, and animation.

The same wireless network that once strained to deliver a 1-bit logo now streams full-colour AVIF heroes, which is exactly the kind of payload-shrinking that helps Core Web Vitals for Images. For the support specifics, see AVIF Browser Support.

Handling a legacy WBMP file

If you inherit a WBMP file, convert it to a current format rather than serving it. ImageMagick reads and writes WBMP:

# WBMP in, PNG out
magick legacy.wbmp logo.png

From there, move the image into the modern pipeline. Convert photos to and from AVIF entirely in your browser — the file never leaves your device:

For two-tone marks that must stay sharp, keep them as PNG. For photographic content, AVIF and its WebP fallback are the right defaults.

Frequently asked questions

Is WBMP still used in 2026? No. WBMP is obsolete; WAP is decommissioned and no current browser renders it.

Can WBMP store colour or grey? No. WBMP is strictly 1-bit — every pixel is either black or white, with no grey, colour, or alpha.

What replaced WBMP? Full mobile browsers replaced it: PNG for graphics, and AVIF or JPG for photographs.

What is WBMP's MIME type? image/vnd.wap.wbmp. Some servers still recognise it, but browsers will not display the image.

How do I open a WBMP file today? Convert it with ImageMagick (magick file.wbmp out.png), since modern viewers and browsers no longer render WBMP directly.

Sources and further reading