How RateSonar records United States rates

RateSonar keeps a dated record of the rates banks advertise. Rate pages are current-state only: when a bank changes a rate the old figure disappears. A record made on the day is the only way to know later what was on offer.

Capture

• Twice a day, from 06:00 and 15:00 America/New York time, each admitted source is requested once, with up to three attempts per slot if it fails.
• Requests identify themselves as RateSonarBot, honour robots.txt (including wildcards), keep at least two seconds between requests to a host, and stop at any block. No log-ins, no forms, no captcha solving and no workarounds. A bank that blocks automated access is listed as such on the coverage page.
• Official rates come from the Federal Reserve (via FRED), the New York Fed, the US Treasury and the FDIC.

Evidence

• The exact bytes of every response are archived with the URL, time, HTTP status and SHA-256 digest. Parsing happens afterwards, from the archive, so a parser fix replays over every past capture.
• Every figure is read by a parser written for that page and checked: it must appear in the page text beside its product, sit inside a plausible band for its product type, and carry a stated basis.
• Rates are stored as the exact decimal the bank printed. APY figures are never ranked against a different basis.

Changes and withdrawals

• A change is a different figure between two captures of the same page and product.
• A product is marked withdrawn only when two complete captures, in different slots, no longer show it. A failed capture never withdraws anything.

How RateSonar differs from comparison sites

Bankrate, NerdWallet and DepositAccounts cover more products and give buying guidance. RateSonar does a narrower job:

• Evidence, not a listing. Every figure links to the bank page it came from, with the time it was read and a digest of the exact bytes.
• History from the first day. Each rate is recorded twice a day, so a change shows when it happened rather than whenever a listing was refreshed.
• No paid placement. Rankings are by rate on one basis, nothing else; RateSonar takes no applications and no referral fees.
• Gaps shown. Banks that block automated reading or publish no public rates are listed by name instead of being left out quietly.
• Built for agents. The same data is a free JSON API and an MCP server, with the date and source on every figure.

Limits

• Coverage is the banks we can read, not every bank in United States. Many large US banks show deposit rates only after a ZIP code; those are listed as not public. Personalised, negotiated and log-in-only rates are out of scope.
• History starts on 1 November 2026, the first day of capture. Nothing earlier is inferred.
• This is not advice. Confirm the rate and its conditions with the bank.