Create Black and White WebP

Strictly, black and white means only two pixel values: pure black (0) and pure white (255). Grayscale means a continuous spectrum. This tool offers both – labelled honestly. Threshold and dither modes produce true 1-bit B&W; grayscale mode produces a luminance gradient.

On Chrome, Firefox, Edge, Opera, and Safari 14+ (≈99% of browsers as of 2026), yes – your output is WebP. The tool detects encoder support at page load and shows a banner. On rare browsers without WebP encode (pre-Safari-14), it falls back to PNG and notifies you in the toast.

Honest answer: it depends. WebP threshold/dither output is typically smaller than the same image as JPEG or color PNG, often by 30-70% – but PNG-1bit can sometimes beat it on stark 1-bit content. Grayscale WebP typically beats JPEG by 25-35% at equivalent quality. The stats line shows your actual before/after numbers. Don’t trust generic “X% smaller” claims without measurement.

Threshold throws away all gray information – every pixel becomes either pure black or pure white. On photos this loses detail in skin tones and gradients. For photos, try Floyd-Steinberg or Bayer dither instead – they’re still 1-bit but use patterns to simulate gray.

Error-diffusion algorithm from Floyd & Steinberg (1976). When a pixel becomes black or white, the rounding error is distributed to neighbouring pixels. Result: 1-bit output that visually approximates the gradient via tiny patterns. The classic newspaper / laser-printer look.

Ordered dither using a fixed 4×4 threshold matrix. Faster than Floyd-Steinberg and gives a characteristic crosshatch pattern – recognisable from Game Boy graphics and Mac System 1/2 displays. Deterministic: same input → same output.

Rec 709 for modern sRGB photos (matches your monitor’s primaries). Rec 601 for legacy SDR / NTSC content (it’s the historical default and what older tools used). Simple average for non-photographic content (screenshots, diagrams).

Yes. WebP supports alpha. Transparent pixels in the source stay transparent in the output. Only RGB channels get B&W’d.

No. Canvas API runs in the browser. Your image never touches any server.

10 MB. Larger images work in principle but the main-thread canvas processing gets slow on big files.