Concatenate multiple files into one
Drop in any files, drag-reorder, and download a single combined blob. Perfect for reassembling File Splitter parts or stitching captured data. Runs entirely in your browser.
No files yet
How to join files
The browser stitches the parts together with a single Blob constructor — no streaming, so all parts must fit in memory.
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Add files
Pick one or many — they queue in selection order.
Inputs are treated as UTF-8 throughout the pipeline and validated client-side as you type — nothing dispatches until the value is well-formed.
inpututf-8client-sidevalidatedfiles · textn · setpart-001 part-002 part-003
loaded · parsedclient-side - 02
Reorder
Drag rows or use ↑ / ↓ to set the join sequence.
Each toggle re-computes through a memoised hook, so flipping options never resets your input and the UI stays snappy on large inputs.
orderoptionslivememoisedtogglesorder · memoiseddrag · livedrag ⋮⋮
options set · memoisedlive - 03
Name the output
Pick a sensible filename and extension.
Randomness — where used — comes from
crypto.getRandomValues, neverMath.random. Heavy work sits inuseMemo.namecomputeinstantlocaldeterministicname · instantout · computedjoined.bin
computed · instantinstant - 04
Join & download
Single click writes the combined blob to disk.
Copy writes through
navigator.clipboardand downloads use aBlob— zero network traffic. Same input plus same options always yield the same bytes.exportcopydownloadzero-networkreproducibleok · copiedready · copiedDownloaded
shipped · ready to shipsuccess
Pro tips for everyday utilities
Reach for crypto.getRandomValues
Cryptographically random for IDs, tokens, salts. Math.random is for animation and games, not security.
Mock data with seeds
Faker-style libraries can be seeded so tests are reproducible. Embed the seed in the fixture file.
Reference cards beat memory
Cheatsheets for Vim, Git, Docker, Linux signals are faster than man pages when you’re mid-flow.
Browser APIs vary
Touch events, gamepads, and clipboard differ across vendors. Feature-detect before use.
Persist in the right place
localStorage for user preferences, sessionStorage for transient state, IndexedDB for structured data.
When to join files
Splitter reassembly, capture stitching, batch combine.
Re-stitch parts
Reassemble files split by File Splitter. Random values come from crypto.getRandomValues — cryptographically secure for tokens, salts, and session IDs. Math.random is deterministic enough for animations but predictable enough to be a security bug.
CSPRNG-backedConcatenated dumps
Glue together multi-segment downloads. Pair with hashids, ULID, or UUID v7 when you need both random and sortable — useful for primary keys, public-facing IDs, and event log ordering without a sequence column.
reproducibleLog stitching
Combine hourly log files into one stream. Output is deterministic given the same seed, so fixtures and tests stay reproducible across CI runs and contributor machines. Embed the seed in the fixture file for full replay.
snappyCapture replay
Merge captured chunks into a single pcap/raw. Heavy work runs through useMemo so the UI stays snappy on large inputs. Same input + same options yields identical bytes — the kind of stability snapshot tests rely on.
feature-detectedBackup batching
Combine pieces of a chunked backup. Storage tools persist to the right backend: localStorage for user preferences, sessionStorage for transient state, IndexedDB for structured data. Pick the right shelf and quota worries disappear.
deterministicAsset bundling
Concat font/image binaries for atlas builds. Browser feature detection: clipboard, fullscreen, gamepad, and Web Bluetooth APIs gracefully fall back when unavailable. No surprise white screens on Safari or older Firefox.
production-readyFrequently asked questions
Something missing?
Tell us what you need. We ship the top requests every two weeks.