If you do not know the name of a knot, KnotFinder can help you. From a diagram of the knot, find its DT Notation. Enter the DT code and click "Find".
KnotFinder is powered by Knotscape, which guarantees to identify any prime diagram with 16 or fewer crossings. (A prime diagram, of a possibly non-prime knot, is one that cannot be directly decomposed into the connected sum of two diagrams both with crossings.) For prime diagrams with 17 or more crossings, any connected summand with crossing number at most 16 that Knotscape identifies is also guaranteed to be correct. Note that KnotFinder cannot distinguish a knot from its mirror image.
For knots with crossing number at most 10, KnotFinder gives the classical Name of the knot instead of the DT Name returned by Knotscape. (For knots with crossing number at least 11, we use the DT Name.)
Knot Sketcher is a Java program, written by Jiho Kim, that lets you draw a knot and returns the DT notation. It requires Java 1.4 to run, and the applet may take a minute to start up. Once you have the DT notation, you can enter it into the search bar above.
Other, more up-to-date knot identification tools can be found elsewhere online, such as these. (Use at your own risk!)
Knot identification can also be done with the programs SnapPy, KnotPlot, and Knotscape.
Knotfinder was built by Jae Choon Cha and C.-M. Michael Wong.