Before you upload
ListSift runs a rules-based QA pass on the batch you provide. Read this before uploading a client list, especially if your agreement limits where that data may be processed.
Open the toolYour pasted or selected CSV is sent over HTTPS to the ListSift application on Cloudflare Workers for analysis. The preview endpoint returns counts and a small set of flagged rows. It does not save the CSV to ListSift's checkout store.
The tool also keeps the CSV and preview in this tab's browser session storage so you can return from a cancelled checkout. Closing the tab normally ends that browser session; you can clear it sooner by clearing the site's session storage.
When you start checkout, ListSift stores the exact CSV in Cloudflare KV with a seven-day expiry, including if you leave checkout unpaid. Stripe hosts card entry. After payment, ListSift asks Stripe whether that Checkout session is complete and paid, then matches it to the stored batch before generating the files.
The success-page URL contains a Stripe session ID that acts as a download key during that retention period. Keep the URL private. Downloads are generated from the stored CSV and sent with no-store cache headers; save your files promptly because ListSift does not provide a permanent account or file archive.
ListSift checks email shape, a short list of role and disposable inbox patterns, domain shape and common weak domains, and repeated email addresses within this CSV. It does not contact mail servers, verify that a mailbox exists, confirm ownership or consent, check suppression lists, or prove that a message will be delivered.
“Valid” and the row confidence score describe ListSift's rules, not mailbox deliverability. A “ready” import row only passes ListSift's file rules; review your target system's current requirements and your own sending permissions before using it.
The paid handoff CSV retains all source columns alongside ListSift's decisions. The smaller HubSpot and Apollo files contain selected import fields and separate rejects files. Keep the original CSV as your source of record.
If you lose the paid link or files fail to release, email support from the checkout address with the approximate payment date and amount. A Stripe receipt or session ID helps if you have one. We check the payment and retained batch before sending a private link back to the checkout address. If verified paid files still cannot be released, the batch charge should be refunded.
ListSift records coarse events such as a preview succeeding, checkout starting, a paid session being verified, and a file being downloaded. An event can include the row-count band, batch grade, or a fixed error or file type. The measurement dataset does not include CSV contents, lead or buyer email addresses, IP addresses, checkout references, or Stripe session IDs. It uses no new browser cookie or tracking identifier.
Cloudflare Analytics Engine retains these event points for three months. Page-request and event totals are directional counts, not unique visitors or purchases; Stripe remains the payment record.