Meento Metadata Bundler

100% client-side — nothing is uploaded to any server. Attach metadata to any file (binary or Base64 text) without corrupting it. The file is returned in the same encoding you sent it in.

Auto-detect treats .txt / .b64 / .base64 files (or names containing "b64"/"base64") as Base64 text; everything else as raw binary.
Metadata
File hash (SHA-256, auto):
Select a file to compute its hash…
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Digital Signature (optional)
Paste your private key (JWK JSON from Meento Key Generator) to sign this file's hash. The signature and your public key are embedded in the metadata so anyone can verify authenticity later — your private key itself is never stored or uploaded anywhere.
Metadata is appended after the file's own content using a small binary footer, so the original bytes are never altered. This works reliably for most common formats (images, PDFs, audio, text, archives, etc.), since readers stop at the format's own end marker. A small number of strict formats that validate exact file size or embed checksums covering the whole file may not tolerate the extra trailing bytes.
Go to Extract Metadata →
Generate a Signing Key →
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