# Re-runs & idempotency

> Submitting the same rows twice, on purpose and by accident.

Section: Campaigns, emails & batches · HTML: https://app.multiplied.studio/docs/campaigns/re-runs-and-idempotency · Index: https://app.multiplied.studio/llms.txt


## On purpose

Submit a new batch under the same email. Same identifier → the new render overwrites the old file at the same URL (or is skipped, or suffixed, per the duplicate policy you chose on upload).

## By accident

Over the API, send an `Idempotency-Key` header with every submit. A retried call with the same key returns the original batch with `replayed: true` and spends nothing. In the app, the wizard keeps a draft, so a refresh mid-flow resumes rather than resubmits.