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Biology Tools · Updated October 21, 2026 · Reviewed by FormatFlow Editorial

Codon Translator

You can translate DNA or RNA sequence into the standard genetic code at reading frame 1, 2 or 3, with mRNA, one-letter and three-letter protein output and a codon-by-codon table.

Runs in your browserFree · No sign-up · No watermark
DNA/RNA → PROTEINRuns in your browser
Loading the tool…

Everything runs locally in this tab. No file is uploaded while the tool loads.

This tool runs in your tab. Nothing is uploaded and no copy is stored.

How files are handled

At a glance

Works with
DNA/RNA → PROTEIN
Processing
In your browser
Price
Free, no account
Updated
October 21, 2026
All Biology Tools

About Codon Translator

A codon is three nucleotides read together, and the standard genetic code maps 64 codons to 20 amino acids and three stop signals. Translation needs a reading frame: the same sequence read from the first, second or third base can give three different protein strings, which is why choosing the frame is part of the question.

This translator cleans DNA or RNA input, transcribes DNA to mRNA, translates every complete codon at the chosen frame and marks stops in both one-letter and three-letter output. A codon table shows position and amino acid, ambiguity codes become X, and bases left after the last complete codon are reported instead of being guessed.

What this tool does

The details that matter when you use Codon Translator for real work.

  • Three reading frames

    Switch between frames 1, 2 and 3 to see how the same sequence translates when reading starts at the first, second or third base.

  • DNA and RNA input

    DNA is transcribed with T → U automatically, while RNA is used as mRNA directly; the detected molecule is reported.

  • One-letter and three-letter protein

    Both output formats are shown and can be copied, with stop codons marked as * or Stop.

  • Codon-by-codon table

    Each row lists the codon number, its first nucleotide position, the mRNA codon and the amino acid.

  • Ambiguity and partial codons

    Codons containing N or another ambiguity code translate to X, and trailing bases are counted instead of being dropped silently.

  • Copy for downstream work

    Copy the mRNA, the one-letter protein or the three-letter list into notes, a report or another tool.

How to use Codon Translator

No account, no installation — the whole job happens in this browser tab.
  1. 01

    Paste the sequence

    Paste raw sequence or a FASTA record; headers, spaces, digits and punctuation are removed before translation.

  2. 02

    Choose the reading frame

    Frame 1 starts at the first base, frame 2 at the second and frame 3 at the third, then reads every third base.

  3. 03

    Check the detected molecule

    DNA is transcribed to mRNA with T → U; RNA is translated directly, and a mixture of T and U is flagged.

  4. 04

    Read the protein

    Use the one-letter string for compact work or the three-letter string for reports, and note where the first stop falls.

  5. 05

    Inspect the codon table

    Check each codon, its nucleotide position and its amino acid; ambiguity codes appear as X with a note.

How this tool works

Works with
DNA/RNA → PROTEIN
Processing
Client-side, in your browser. Nothing is uploaded.
Requirements
Chrome, Edge, Firefox or Safari · JavaScript enabled

Limitations worth knowing

  • Uses the standard genetic code only; mitochondrial and alternative genetic codes are not modelled.
  • Ambiguity codes translate to X, so a stop codon hidden behind an ambiguous base cannot be detected.
  • The table lists codons after the first stop for inspection; the tool does not model splicing, frameshifting, RNA editing or post-translational modifications.

Privacy and file handling

The sequence you paste stays in this browser tab. Cleaning, transcription and translation run with JavaScript on your device, so nothing is uploaded, stored or logged, and closing the page discards the input and the result.

Read the full privacy policy

Codon Translator FAQ

Short, direct answers to the questions people ask before using this tool.
What is a reading frame?
The reading frame decides where the three-base grouping starts. Starting at the first base, the second base or the third base produces three different sets of codons, and therefore potentially three different protein sequences from the same nucleotides.
What genetic code does this translator use?
It uses the standard genetic code, the human nuclear code, with all 64 codons and three stop codons. Mitochondrial codes and other variant codes differ in a few codons and are not modelled here.
How are stop codons shown in the output?
Stops are written as * in the one-letter protein and as Stop in the three-letter output, and the codon table highlights the stop rows. The first stop is also reported, because translation normally ends there in a cell.
What happens when the sequence contains N or another ambiguity code?
The codon cannot be resolved, so it translates to X in one-letter output and Xaa in three-letter output, with the count of ambiguous codons reported. A stop codon hidden behind an ambiguity code therefore cannot be detected.
Why does the same sequence give a different protein in frame 2?
Shifting the frame by one base changes every codon after that point, so the amino acid sequence is unrelated. Only one frame usually corresponds to the real protein; the others are reported so you can compare them.
Does the tool stop translating after the first stop codon?
The protein strings list every complete codon in the frame, with stops marked, and the first stop is called out separately. That lets you inspect the rest of the sequence while still showing where translation would normally terminate.
What happens to bases that do not fill a complete codon?
Bases after the last complete codon are counted and reported as trailing bases rather than translated or discarded silently. If the sequence is shorter than one codon at the chosen frame, the tool says so instead of showing an empty protein.
Is my sequence uploaded or stored anywhere?
No. Cleaning, transcription and translation all run with JavaScript in this browser tab, so the sequence is never uploaded, stored or logged, and closing the page discards it.

Background reading

Format guides that explain the trade-offs behind Codon Translator.