SHA256 Online Base64: Convert a Digest Between Hex and Base64

The two representations

Hex spells each byte as two characters — 64 characters total. Base64 packs three bytes into four characters — 44 characters with the trailing "=" padding, 43 without.

Base64url, used in JWTs and URLs, swaps + and / for - and _ and usually drops the padding. If a digest contains hyphens or underscores, it is base64url and must be translated before a standard decoder will read it.

Producing Base64 directly

The essential step is hashing to raw binary before encoding, rather than encoding the hex string:

# shell
openssl dgst -sha256 -binary file.txt | base64

# PHP — third argument returns raw bytes
base64_encode(hash('sha256', $data, true));

# Python
import base64, hashlib
base64.b64encode(hashlib.sha256(data).digest())

If your result is 88 characters, you Base64-encoded the 64-character hex string by mistake. The correct output is 44.

Where each format is expected

Base64: Subresource Integrity attributes in HTML (integrity="sha256-..."), HTTP Digest headers, JWT signatures, certificate pinning entries, Kubernetes manifests.

Hex: command line checksums, package manifests, Git object ids, database columns, anything a human compares by eye.

When a spec shows a digest with a sha256- prefix and characters like + or /, it wants Base64 — pasting hex there silently fails the check.