Deploy code

Open a canister’s Code section to see what it runs and deploy new code. You need to control the canister, yourself or through an Agent.

See what it runs

• History lists recent code changes.
• Version comes from the module’s own metadata, when it publishes one.
• Verify build compares the module hash with a file or hash you provide. A match proves the bytes are identical.

Deploy

Reinstall and uninstall erase data

Take a snapshot first. It’s the only way back.

1. Choose Deploy code and select a .wasm or .wasm.gz file (up to 100 MiB).

2. Choose the mode:

   Mode	Does
   Install	Puts code into an empty canister.
   Upgrade	Replaces the code and keeps the canister’s data.
   Reinstall	Replaces the code and erases the data. Needs a recent snapshot.

3. Add the install argument, if any, as hex.

4. Review and confirm. If both interfaces are known, the review warns you when the new one breaks the old.

Large modules upload in chunks. If you’re interrupted, choose Save and exit and resume later with the same file. You can also stop the canister before installing and start it again after.

Stop, start, uninstall and delete

• Stop and Start pause and resume the canister. Its code and data stay.
• Uninstall code removes code and data, but keeps the canister and its cycles. You can take a snapshot first, in the same review.
• Delete (in Settings and access) removes the canister. Its cycles above 1 TC plus its freezing reserve are sent back to your cycles account first.

Each one opens its own review. Uninstall and delete ask you to type the canister’s name.

Good to know

• If a deploy’s result is unclear, check the module hash before deploying again. Never reinstall to find out: it erases data.
• Deploys you started in this browser can be resumed only here, as the same identity.