Body Swap

Keep several named bodies on one request. Switch, send, done.

A Yaak plugin for everyone who tests the same endpoint with more than one payload (the happy path, the missing field, the huge one) and is tired of pasting bodies in and out of the editor or keeping a graveyard of Create user (copy 3) requests in the sidebar.

A variant is a snapshot of the request’s body and body type, stored without interpreting its shape: JSON, GraphQL, form-encoded, and multipart bodies all work.

The four actions

Right-click a request in the sidebar, or open the command palette while the request is active:

Action	What it does
Save Body as Variant	Snapshots the current body under a name. Same name updates it.
Switch Body Variant	Puts the chosen body on the request. The plain Send button now sends it.
Send Body Variant	Switches to the chosen body, then sends it in one step.
Delete Body Variant	Removes a snapshot. Your current body is untouched.

A one-minute tour

1. Write a valid payload in the body editor → Save Body as Variant → name it valid.
2. Break it (remove a required field) → Save Body as Variant → missing-email.
3. Send Body Variant → pick valid → the request fires and the editor shows exactly the body that produced the response.
4. Switch Body Variant whenever you want a different body active without sending anything.

Small things it gets right

• The picker knows which variant is active. Dialogs preselect the variant matching the request’s current body: the one you last switched to. Confirm without touching the select and it acts on that one.
• The editor never lies. Sending a variant switches to it first, so the body on screen is always the body behind the newest response.
• Every body type. Snapshots are opaque: multipart and form bodies survive the round trip exactly like JSON.
• Templates keep working. Variants store your ${[ ... ]} tags unrendered; they render with the active environment at send time, like any other body.

Install

From the plugin registry: search for Body Swap in Settings → Plugins.

From source:

npx --yes @yaakapp/cli plugin build

then Settings → Plugins → Add Plugin → choose this directory.

Good to know

Variants live in Yaak’s plugin store (your local database), keyed by request id:

• They stay on this machine: workspace export, import, and directory sync don’t carry them.
• Re-importing a spec (OpenAPI etc.) creates requests with fresh ids, so regenerated requests start without variants.
• Deleting a request in Yaak leaves its variants behind in the store; the plugin API has no deletion event to clean up on.
• Switching replaces the request’s current body by design. If the current body matters, save it as a variant first. The switch dialog reminds you.

Development

Node 24 is required by the plugin bundler (.nvmrc included). Note that npx yaak resolves to an unrelated npm package. Always use npx --yes @yaakapp/cli.

npm install
npx vitest run                        # tests
npx tsc --noEmit                      # typecheck
npx --yes @yaakapp/cli plugin dev     # rebuild + reload into Yaak on save

Without plugin dev, a statically installed plugin does not reliably pick up rebuilds. Restart Yaak or toggle the plugin off and on after building.