JSZipp - ZIPs in the modern browser
Fast, compact, and defensive.

Demo route
Write, inspect, stream, then harden an untrusted ZIP.
This mirrors the browser trust-boundary workflow described in the docs.
Current run
Queue
0
entries queued
Output
0 B
archive bytes
Savings
—
after compression
CRC sample
pending
first file check

Forge an archive

ZipWriter.add → close
Archive
6
Ready. Toggle samples and forge.

Compression

original vs. stored bytes
Forge an archive to watch each entry compress.

Archive map

openZip().entries
0
No archive open.

Entry reader

text() · bytes() · arrayBuffer()
Select an entry to read it three ways and verify its CRC‑32.

Streaming writer

ZipTransformStream

Entries written into .writable become ZIP bytes on .readable as you go — watch bytes leave before the last entry is even added. Nothing buffers the whole archive.

1 writing into .writable

Press run to feed entries in.

2 emitted from .readable

0 B
Byte chunks appear here in real time.

Read it back, one entry at a time

readZipStream()

for await (const entry of readZipStream(…)) pulls each entry forward-only: read text, skip binaries & directories, never seek back.

Run the streaming build (or forge / open an archive), then scan.
Each card crafts a real malicious archive, then opens it twice: once unguarded and once through a JSZipp guard option. Watch the guard slam shut while the naïve path lets the payload through. 0 / 4 blocked
jszipp · live api trace