About this tool
Paste a nucleotide sequence to compute its reverse complement — the sequence of the opposite strand read in the 5′→3′ direction. The input is uppercased and limited to valid bases and IUPAC ambiguity codes. It runs entirely in your browser.
Each base is complemented using an IUPAC-aware map: A↔T, G↔C, plus ambiguity pairs such as R↔Y, K↔M, W↔W, S↔S, B↔V, D↔H and N↔N. The complement is that map applied base by base, the reverse is the sequence written backwards, and the reverse complement is the complement written backwards. In RNA mode the output uses U instead of T.
All three results are shown, with the reverse complement highlighted and copyable. For example, GATTACA has the complement CTAATGT and the reverse complement TGTAATC.
Frequently asked questions
What is a reverse complement?
It is the sequence of the complementary strand read from its 5′ end. You complement each base (A↔T, G↔C) and then reverse the order, giving the antiparallel partner strand.
Does it support IUPAC ambiguity codes?
Yes. Degenerate bases such as R, Y, S, W, K, M, B, D, H, V and N are complemented to their correct partners (for example R↔Y and K↔M).
What is the difference between the three outputs?
Complement swaps each base without reordering; reverse writes the original sequence backwards without swapping; reverse complement does both.
How does RNA mode differ?
In RNA mode the output uses uracil (U) in place of thymine (T); the complementation rules are otherwise identical.