How do I verify a SHA-256 checksum on Mac, Windows, or Linux?

Open PDFFlare's verify checksum online tool, paste the SHA-256 hash from the publisher (a 64-character hex string), then drag your downloaded file into the upload area. The tool auto-detects that the hash is SHA-256, computes the file's SHA-256 in your browser, and compares the two. Green ✓ Match means the download is authentic; red ✗ Mismatch means re-download. Works identically on macOS, Windows, and Linux because everything runs in your browser — no platform-specific tooling needed.

Does this verify ISO checksums for Linux distros like Ubuntu, Fedora, or Debian?

Yes. Linux distros publish SHA-256 (and often SHA-512) hashes on their download pages and in SHA256SUMS files. Copy the hash for your specific ISO, paste it into the Expected hash field, drop the .iso file, and PDFFlare confirms the match before you flash it to a USB or burn a disc. This is the safest way to catch corrupted downloads or man-in-the-middle tampering before installing an OS.

Can I verify a hash from a SHA256SUMS file directly?

Yes — PDFFlare understands SHA256SUMS-style lines. If you paste `a1b2c3... filename.iso` (the full line from a SHA256SUMS file, including the filename), the tool keeps just the hash portion and ignores the rest. You can also drop the SHA256SUMS or .sha256 file itself into the companion drop zone (expand the disclosure below the verdict) and PDFFlare extracts the hash automatically.

What if the publisher gives me a base64 hash, not hex?

PDFFlare accepts both. Hex is the most common format (used by Linux SHA256SUMS files, GitHub releases, sha256sum/Get-FileHash output), but some publishers (Apache projects, certain Java tools) publish base64-encoded digests. The tool detects which encoding you pasted by trying hex first, then base64 — and decodes base64 to verify against your file's hex digest. The verdict is the same either way.

Why does the tool need to auto-detect the algorithm?

Because every hex hash length is unique to one algorithm — 32 chars is always MD5, 40 is SHA-1, 64 is SHA-256, 96 is SHA-384, 128 is SHA-512. PDFFlare counts the hex characters you pasted and picks the right algorithm automatically. You can override the choice from the dropdown if the publisher used an unusual format, but in practice the auto-detect is correct 100% of the time for properly formatted hashes.

Is the comparison resistant to timing attacks?

Yes. PDFFlare uses constant-time comparison: every character of the expected and actual hash is XOR'd, and the differences are OR'd into a single value. Total comparison time is identical for any two strings of the same length, regardless of how many characters match. This is overkill for client-side verification (no attacker is timing your browser), but it costs us nothing to do correctly and matches what proper server-side hash comparison libraries do.

What does a mismatch mean — is the file dangerous?

A mismatch means the file you have is NOT byte-identical to what the publisher signed. Three causes: (1) corrupted download — incomplete bytes from a flaky network, common with large ISOs; (2) wrong file — you may have grabbed an older build, a different architecture, or a sibling release; (3) tampering — a malicious mirror or MITM swapped the file. The fix is the same: re-download from the original source over HTTPS and verify again. If multiple downloads from different mirrors all mismatch, contact the publisher.

Is the file uploaded to PDFFlare's servers?

No. The file is read via the browser's File API and hashed locally with `crypto.subtle.digest()` (for SHA algorithms) or a small client-side MD5 implementation. Nothing leaves your machine. Open your browser's Network tab while running the verify — you'll see zero requests to pdfflare.com during the hash computation. This is what makes the tool safe to use for confidential or proprietary file verification.

Can I verify multiple files in batch?

Not in this tool — it processes one file at a time so the verdict UI stays clear. For batch verification of dozens of files (e.g., verifying every entry in a SHA256SUMS file), use command-line `sha256sum -c SHA256SUMS` on Linux/macOS or `Get-FileHash` loops in PowerShell. PDFFlare's verify checksum tool is best when you have one specific download to confirm — quick, visual, no install required.

What's the difference between this and the File Checksum tool?

Both work on file bytes, but the intent is different. File Checksum computes all five hashes (MD5/SHA-1/SHA-256/SHA-384/SHA-512) and shows them — useful when you need to publish a hash or copy one. Verify Checksum takes a hash you already have from the publisher and tells you yes-or-no whether the file matches — the verdict-first UX is optimized for the common case of confirming a download. Use whichever matches your starting point.

Verify Checksum Online — SHA-256, MD5 File Verifier

Verify checksum online — paste a SHA-256, MD5, or SHA-512 hash and match it against your file. Auto-detects algorithm. Browser-only, no upload.

PDFFlare's verify checksum online tool gives you a one-step yes-or-no answer: does this file match the hash the publisher published? Paste the hash, drop the file, and the tool runs a constant-time comparison and shows a big green ✓ Match or red ✗ Mismatch. Use it as a sha256 hash verifier for ISO downloads, an md5 hash checker for legacy software, or a generic checksum verifier online when you need to confirm a download is byte-perfect before installing it.

The tool auto-detects the algorithm by hex length — 64 chars is SHA-256, 32 is MD5, 128 is SHA-512 — so a single field handles every common format. SHA256SUMS-style lines (`abc… filename.iso`) work too: PDFFlare keeps just the hash portion. To compute fresh hashes from scratch instead of verifying an existing one, use the File Checksum tool; for HMAC signatures over webhook bodies, the HMAC Generator handles that. Hashing strings or JWT payloads is the Hash Generator.

Acts as a verify file integrity online utility, sha256 checksum verifier, compare file hash tool, and verify iso checksum companion — all in one page. Files are read locally via the browser's File API and hashed with Web Crypto; nothing uploads. Free, unlimited, no signup.

Drop the file to verify

Any file — ISO, ZIP, installer, archive. Hashed entirely in your browser.

Expected hash

Algorithm

Hex length tells us the algorithm — 64 chars = SHA-256, 32 = MD5, 128 = SHA-512. Override only if the publisher used an unusual format.

Drop a file above and paste a hash to verify.

Have a .sha256 / SHA256SUMS file? Drop it here.

Drop a SHA256SUMS / .sha256 file or click to browse

We'll read the text contents into the expected-hash field above. Then drop your actual file at the top to verify.

Your file is hashed entirely in your browser using crypto.subtle.digest()for SHA + a small client-side MD5 implementation. Comparison is constant-time so a timing side-channel can't leak the expected hash. Nothing is uploaded.

How to Verify a File Checksum

Paste the published hash
Copy the SHA-256, MD5, or SHA-512 hash from the publisher's release page, SHA256SUMS file, or download notes. Paste it into the Expected hash field. PDFFlare auto-detects which algorithm it is by counting the hex characters — 64 = SHA-256, 32 = MD5, 128 = SHA-512.
Drop the file
Drag the file you downloaded into the upload area, or click to browse. Works with any file type — ISOs, ZIPs, installers, archives, packages. The file is hashed entirely in your browser, never uploaded.
Read the verdict
PDFFlare runs the comparison in constant time and shows a big green ✓ Match if the file is authentic, or a red ✗ Mismatch if the hashes differ. On a mismatch, the tool also displays both the expected and actual hash so you can see exactly where they diverge.
Re-download or proceed
Match means the download is byte-perfect — install with confidence. Mismatch means the file is corrupted, tampered with, or you grabbed the wrong build — re-download from the original source and verify again. Recent verifies (filename + verdict only) are remembered for your next visit.

When Do You Need to Verify a Checksum Online?

Before flashing a Linux ISO: Every major distro (Ubuntu, Fedora, Debian, Arch, Mint, Pop!_OS) publishes a SHA-256 hash for each release ISO. Verifying before you write the image to USB catches truncated downloads, swapped mirrors, and rare-but-real MITM tampering. Use this verify iso checksum tool to get a green ✓ before dd or Rufus, not after.

Verifying GitHub release artifacts: Many open-source projects ship a checksums file (often `SHA256SUMS` or `release.sha256`) alongside the binary tarballs. Drop the downloaded artifact, paste the corresponding hash, and confirm in one click. PDFFlare auto-handles SHA256SUMS-line format so you can paste the full line including the filename.

Confirming Windows installer + macOS DMG integrity: Software vendors sometimes publish a SHA-256 fingerprint alongside the .exe / .msi / .dmg download. PowerShell's `Get-FileHash` and macOS's `shasum -a 256` can compute the local hash, but pasting it side-by-side with the expected hash in a small terminal window is error-prone. The verify checksum online interface gives you a clear green / red verdict instead of eyeballing two long hex strings.

Confirming a backup or archive transferred intact: Copied a 50 GB backup to a new drive or uploaded to cold storage? Hash the original (with File Checksum), then bring it back later and use this Verify tool to compare against the destination — if it matches, every byte made the trip. Catches silent disk corruption, partial uploads, and copy errors that may not surface until you try to restore.

Why Use PDFFlare to Verify a Checksum?

Verdict-First UX

A big green ✓ Match or red ✗ Mismatch is the hero output — no eyeballing two hex strings side-by-side. On mismatch, the tool shows both hashes so you see exactly where they diverge.

Auto-Detects the Algorithm

32 hex chars → MD5. 64 → SHA-256. 128 → SHA-512. The tool picks the right algorithm from the hash you paste, with a manual override for unusual cases. Hex and base64 both supported.

100% Browser-Based

Web Crypto handles SHA digests; a small local module handles MD5. Files are read via the File API — nothing uploads. Safe for sensitive backups, internal builds, and proprietary downloads.

No Signup Required

Free, unlimited, no account, no rate limits. Constant-time comparison, SHA256SUMS-line parsing, and recent-verifies history (filename + verdict only — never the hash) all included.

Frequently Asked Questions About Verify a File Checksum

Password Generator

Random, passphrase, PIN

UUID Generator

v1, v4, v5, v7 + bulk

HMAC Generator

HMAC-SHA256 webhook signatures

File Checksum

MD5 + SHA hashes of any file

Random Secret

JWT secrets, API keys, webhook keys

Hash Generator

MD5, SHA + HMAC signing