A SWIFT code has a structure you can read, which makes it one of the few payment identifiers you can partly check with nothing but your eyes. Eight or eleven characters, in a fixed layout, with a country code sitting in the middle of it. That gets you a long way before any lookup is involved, and it is the part most checkers do not bother to explain.
Read the four blocks first
A BIC is four letters identifying the institution, then two letters that are the ISO country code, then two characters for the location within that country, and optionally three more for a specific branch or department. So a code with GB in positions five and six is a United Kingdom institution and a code with US there is an American one, whatever the rest says. If the country block does not match the country you are sending to, stop there. That single check catches a surprising share of wrong codes.
Then match it to the bank's own page
Most banks publish their own BIC on a help page aimed at exactly this question, because their customers are constantly being asked for it. HSBC, NatWest, Nationwide, Lloyds, Bank of Scotland, the Co-operative Bank, Santander, Monzo and Starling all publish such a page in the UK. Finding the bank's own page and reading the code off it is stronger than any third party lookup, because it is the institution stating its own identifier rather than a database repeating one.
What a checker cannot do
It cannot tell you that the code belongs to the branch that holds the account, and it cannot tell you that the account exists. Large banks have many BICs, including branch specific eleven character forms, and a payment sent with the head office code where a branch code was required will usually still arrive but can be delayed while it is repaired. There is no international equivalent of the UK name check, so the name on an international payment is not verified before it leaves.
A practical routine
Ask the recipient for the code in writing and ask them to include the IBAN. Read the country block and confirm it matches. Search for the recipient bank's own help page and confirm the code appears there. If it does not, ask the recipient to confirm it with their bank rather than assuming a directory is right. For a first payment to a new recipient, send a small amount and wait for confirmation before sending the rest.
Questions people ask about swift code checker
How many characters should a SWIFT code have?
Eight or eleven. Eight identifies the institution and its main location, and eleven adds a three character branch or department code.
Is SWIFT code the same as BIC?
Yes in everyday use. BIC is the formal name of the identifier and SWIFT is the network that made it familiar, so banks use both words for the same code.
Can I check a SWIFT code for free?
You can check its structure yourself and confirm it against the bank's own published page, which costs nothing. The full institution directory is a licensed product.
What happens if I use the wrong SWIFT code?
The payment is usually returned or repaired, which costs days and sometimes a fee. It will not normally reach a different account, because the IBAN identifies the account.