Getting the PDF
In Capital One online banking, statements are usually under View statements, on the account page. Download the PDF itself; a screenshot or a scan will not work.
What the tool reads in a Capital One statement
Card statements with a transaction date and a posting date on each line (the posting date is used), month-name dates such as "Sep 25", and payments shown as negatives.
Before comparing anything, the tool adds the lines it read to the beginning balance and checks the result against the ending balance printed on the statement. If they disagree it says so, instead of guessing.
Files are read inside your browser tab. Nothing is uploaded, no account is needed, and nothing is saved: closing the tab clears everything. The processing code is open source.
nildiff is independent and is not affiliated with or endorsed by Capital One. Bank names are used only to describe statement layouts.