Guides

Day-to-day flows in the Spanline app. For the first capture, see Getting started.

Create an Inbox

Open Capture from the product rail (or Home → continue Capture).
Choose New Inbox in the context bar when you want a fresh catch URL.
Optionally set the default mock response (status, headers, body, delay) and link a Project.
Copy the catch URL after creation.

New Inbox modal with response options and project picker — New Inbox — default mock response, optional project link, and create action.

Optionally assign a Project in the product so related work stays grouped.

Receive traffic

Paste the catch URL into your provider’s webhook settings, or send a test request with any HTTP client.
Confirm the request appears in the sidebar list.
Open a request to inspect headers, body, and timing.

curl -X POST "https://api.spanline.dev/i/<your-inbox-id>" \
  -H "Content-Type: application/json" \
  -d '{"event":"demo"}'

Response headers from Spanline include a request id you can use when correlating with the sender’s logs.

On an empty Inbox, use Send test or copy a snippet from the listen hero:

Empty inbox with listen hero and client snippets — Listen hero — **Send test** and stack-specific snippets while you wait for traffic.

Inspect requests

Open Capture and select an Inbox (switch from the context bar if you have several).
Choose a request in the sidebar.
Use the inspector tabs: Body (text / binary), Headers, Query, Cookies, Auth, Meta.
Use Help for your catch URL and any limits shown for your workspace.

Capture console with request selected — Inbox console — sidebar list, catch URL, and **Inspect** tab with request detail.

Inspector tabs

Tab	What you see
Body	JSON, text, or hex for binary payloads
Headers	Incoming request headers (and response headers in the rail)
Query	Parsed query parameters
Cookies	Cookie header breakdown
Auth	Detected API keys, Bearer tokens, basic auth
Meta	Timing, client address, request id

Request inspector Body tab with JSON payload — Body — formatted JSON from a payment-style webhook.

Request inspector Headers tab — Headers — every header the sender included.

Request inspector Auth tab — Auth — detected credentials for quick review (use test tokens only).

Configure a mock response

Decide what callers receive while you debug:

HTTP status
Response headers and body
Optional delay (reflected in timing)

Open the Response tab in the console. Pick a preset (JSON 200, empty 204, 401 auth challenge) or edit fields directly. Changes save to the Inbox on the server.

Capture Response tab with mock response editor — Response — default status, headers, body, and delay for every catch hit.

Capture also allows browser-based tests from other origins when you need them.

Replay a request

Open a request → Replay (same catch URL) or Edit & Replay (tweak method, path, target, headers, body first).

Edit and Replay modal — Edit & Replay — adjust the captured request before sending from your browser.

Prefer relative replay when testing against the same path context.
Use an absolute URL only for trusted targets — replayed requests may still carry original auth headers.

Replay runs from your browser; it is not a server-side replay API.

Compare two requests

From request detail, open Compare (or add ?compare=1 to the URL). Pick a second request from the same Inbox and review header and body diffs.

Compare drawer with header diff — Compare — side-by-side headers and body between two captured requests.

Export HAR

From request details, use the export menu to download a HAR file. You can export the current request or the full session. HAR includes timing through the response Spanline served (including any configured delay). Handy for sharing with partners or importing into other tools.

Clean up

From the Inbox you can:

Delete a single request (sidebar row menu)
Clear all requests in the Inbox
Delete the Inbox when you are done (Inbox switch → destroy)

Delete Inboxes that received production-like secrets when the investigation is finished.