Create an alpha-aware ThumbHash for progressive image interfaces using the reference DCT layout. The browser scales the decoded WebP within the algorithm's 100-by-100 bound, composites color as specified, encodes luminance, chroma, and optional alpha coefficients, and returns the exact bytes plus Base64.
How to use WebP ThumbHash Generator
- Choose static WebP files; transparent pixels are included in the alpha-aware encoding path.
- Generate the hash locally from a bounded proportional sample.
- Store the Base64 value and decode it with a compatible ThumbHash implementation to render a small placeholder before the full image arrives.
What this tool is good at
When to use WebP ThumbHash Generator
Ship a deliberate ThumbHash workflow
Store a compact alpha-aware binary placeholder with approximate aspect-ratio information for progressive loading in apps and image-heavy interfaces. Base the result on the selected WebP's real bytes, decoded pixels, filename, or intrinsic dimensions instead of pasting a generic example that may not match the production asset.
Create an auditable engineering handoff
Persist the returned Base64 exactly, decode it with an interoperable ThumbHash library, and size the placeholder container from the real asset dimensions when available. Save the generated code, report, hash, placeholder, or reconstructed file with the related ticket so another developer can verify inputs and reproduce the decision.
Protect private source imagery
Process client, product, campaign, and internal WebP assets in the current browser tab without submitting selected image bytes to a remote conversion or analysis service.
How to choose the right settings
Start from the consuming system
Persist the returned Base64 exactly, decode it with an interoperable ThumbHash library, and size the placeholder container from the real asset dimensions when available. Confirm the real template, CSS layout, storage field, command-line version, caching policy, and browser target before treating generated defaults as production-ready.
Review size and runtime cost
Store a compact alpha-aware binary placeholder with approximate aspect-ratio information for progressive loading in apps and image-heavy interfaces. Compact source files can expand into long text, while hashes and inlined placeholders transfer work or bytes into HTML, CSS, application state, or client-side decoding.
Keep the original until verified
ThumbHash is not a duplicate detector or file digest, cannot reconstruct source pixels, and omits animation, metadata, and precise color-management information. Retain the authoritative source and test the result in its destination before replacing any deployed asset or automation step.
Practical workflow and output details
The decoded image is proportionally bounded to 100 pixels, transformed into luminance, chroma, and optional alpha channels, then encoded with the standard DCT coefficient layout. All transformation and analysis work uses bounded browser APIs, Canvas, typed arrays, or local Blob creation; only static application resources are fetched.
ThumbHash is not a duplicate detector or file digest, cannot reconstruct source pixels, and omits animation, metadata, and precise color-management information. The tool deliberately states what it does not generate, execute, deploy, prove, or preserve so a focused developer utility is not mistaken for a complete build pipeline or compatibility guarantee.
Format behavior and limitations
ThumbHash is designed for a tiny blurred preview and intentionally cannot reconstruct the original image or compressed WebP bytes.
The generator encodes one static decoded image; animation, metadata, ICC interpretation outside browser decoding, and pixel-perfect transparency are not retained.
Frequently asked questions
Is ThumbHash the same as BlurHash?
No. Both are visual placeholders, but ThumbHash uses a compact binary format with alpha and approximate aspect-ratio support.
Why Base64 the hash?
The standard result is binary bytes; Base64 makes those bytes convenient to store in text fields or JSON.
Can it verify duplicate images?
No. ThumbHash is perceptual placeholder data and is not a stable content digest.
Related WebP tools
WebP BlurHash Generator
Encode decoded WebP pixels into an interoperable BlurHash string with configurable horizontal and vertical DCT components.
WebP LQIP Generator
Create a genuine tiny WebP low-quality placeholder plus a data-URI snippet using bounded width and quality controls.
Dominant-Color Placeholder
Find a weighted dominant decoded color and generate CSS placeholder variables with contrast guidance and measured color coverage.