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Expasy Translate converts a DNA or RNA sequence into a protein sequence in your browser. You paste a nucleotide sequence, choose which strand and genetic code to use, and read the translation in each frame with open reading frames highlighted. This guide is for researchers who need to translate DNA to amino acid sequence quickly and avoid the most common mistake: using the wrong genetic code. It follows the tool page at web.expasy.org/translate as read on 2026-11-07.
What Expasy Translate is used for in research
The page describes the tool as one that “allows the translation of a nucleotide (DNA/RNA) sequence to a protein sequence”. It is run by the SIB Swiss Institute of Bioinformatics as part of Expasy, which its terms of use describe as hosting over 160 databases and software tools. Typical uses are checking what a cloned insert or a sequenced region encodes, looking at all frames of an unannotated stretch of DNA, and producing a protein sequence to hand to another Expasy tool.
Translate works in one direction only: nucleotide to protein. It does not turn a protein sequence back into DNA. A protein cannot be mapped to a single DNA sequence because most amino acids are encoded by more than one codon, so reverse translation is a different kind of task from this one. If you want to find open reading frames in a sequence and filter them by length, see what an open reading frame is and how to find one with NCBI ORFfinder.
Access Expasy Translate (official source only)
Translate runs on the Expasy web server at https://web.expasy.org/translate/. Nothing is installed. The page header links to Home, Programmatic Access and Contact. The Expasy terms of use (revised 2025-10-01) state that each tool’s own licence applies, that tools are offered “as is” without a guarantee of accuracy, and that the SIB name may not be used for promotion without written approval. Treat the output as a computed translation to be checked against your own design or annotation, not as a validated result.
Step-by-step: translate a DNA or RNA sequence
- Open the Translate page and find the box labelled DNA or RNA sequence. Paste your nucleotide sequence there.
- Under DNA strands, choose forward or reverse. Choose reverse when the coding sequence you care about lies on the opposite strand to the sequence you pasted.
- Pick a genetic code. Choose the code that matches the organism and compartment your sequence comes from; the Standard code is NCBI’s Table 1 (see the comparison below).
- Pick an output format (Verbose, Compact, or one of the two options that include the nucleotide sequence).
- Submit the form. The page shows a section headed Results of translation.
- In the results, find the frame that contains the open reading frame you expect. Open reading frames are highlighted in red. Select your initiator on that frame to retrieve its amino acid sequence.
Options exactly as the page words them
| Control | Choices on the page |
|---|---|
| Input | A box for a “DNA or RNA sequence” |
| DNA strands | forward; reverse |
| Output format: Verbose | Met, Stop, spaces between residues |
| Output format: Compact | M, -, no spaces |
| Output format: with nucleotides | Includes nucleotide sequence; Includes nucleotide sequence, no spaces |
| Genetic code | Standard (only A, C, G, T); a series of mitochondrial and nuclear alternatives (including vertebrate, yeast, mold/protozoan/coelenterate, invertebrate, ciliate, echinoderm/flatworm, euplotid, alternative yeast, ascidian, blepharisma, chlorophycean, trematode, Scenedesmus obliquus and pterobranchia); Standard + ambiguous DNA (R, Y, N, S, W, K, M, D, V, H, B) |
The genetic-code selector links to the NCBI genetic codes page, which is the reference for what each option means.
Choosing the genetic code: why it changes your protein
The NCBI page “The Genetic Codes” (Elzanowski and Ostell, updated 2024-09-23, read 2026-11-07) lists 27 numbered translation tables. Table 1 is the Standard Code and is the default for GenBank coding sequences. Table 2, the Vertebrate Mitochondrial Code, differs from it at four codons:
| Codon | Table 1 (Standard) | Table 2 (Vertebrate Mitochondrial) |
|---|---|---|
| AGA, AGG | Arginine | Stop |
| AUA | Isoleucine | Methionine |
| UGA | Stop | Tryptophan |
So a vertebrate mitochondrial gene translated with the Standard code will read UGA as Stop where the mitochondrial code reads Trp, and AGA/AGG as Arg where the mitochondrial code reads Stop. The same sequence translated with the vertebrate mitochondrial code gives a different protein. Pick the code that matches the genome the sequence came from. Note the Standard option on Translate accepts only A, C, G and T; if your sequence contains ambiguity symbols, use the Standard + ambiguous DNA option instead.
Output and how to read it
- Frames. The translation is shown frame by frame under “Results of translation”. An unannotated sequence has no stated reading frame, so look at all frames and use the highlighted open reading frames to decide which is the real one.
- Highlighted open reading frames. Open reading frames are shown in red.
- Residue notation. Verbose output writes Met and Stop with spaces between residues; Compact output writes M and a dash for stop with no spaces.
- Initiator selection. Choosing an initiator on a frame retrieves that amino acid sequence. It is displayed as a pseudo-entry in FASTA format, which you can download as FASTA or as text.
- Hand-off to other tools. From the result you can send the sequence straight to ProtParam, ProtScale, Compute pI/Mw, PeptideMass and PeptideCutter. For composition, molecular weight and pI, see ProtParam: computing protein properties from a sequence.
Troubleshooting
The protein stops early or has unexpected residues
Check the genetic code first. A mismatch between the code and the source genome (for example Standard code applied to a vertebrate mitochondrial sequence) changes the meaning of AGA, AGG, AUA and UGA, as in the table above.
The sequence contains letters other than A, C, G, T
The Standard option on the page is labelled “only A, C, G, T”. Choose Standard + ambiguous DNA, which covers R, Y, N, S, W, K, M, D, V, H and B.
The translation looks like nonsense in every frame
Your coding sequence may be on the other strand. Repeat the run with DNA strands set to reverse.
You have a protein and want DNA (reverse translate)
Translate cannot do this; it takes nucleotide input and gives protein output. Use a tool built for reverse translation, and remember the result is only one of many possible coding sequences.
Free alternatives for translating nucleotide sequences
| Tool | What its own documentation says |
|---|---|
| EMBOSS transeq | “reads one or more nucleotide sequences and writes the corresponding protein sequence translations to file.” Frame option takes 1, 2, 3, F (forward three frames), -1, -2, -3, R (reverse three frames) or 6 (all six frames), default 1. Output is protein FASTA-style with a frame suffix on each name; stop codons are marked with an asterisk. Source: EMBOSS 6.6 documentation, read 2026-11-07. |
| NCBI ORFfinder | “ORF finder searches for open reading frames in the DNA sequence you enter.” Input is an accession number, gi or nucleotide sequence in FASTA format. Minimal ORF length options are 30, 75, 150, 300 and 600 nt; start codon options are ATG only, ATG and alternative initiation codons, or any sense codon; the genetic code can be chosen. Source: ncbi.nlm.nih.gov/orffinder, read 2026-11-07. |
Sequence-analysis suites can also translate sequences locally; see Geneious Prime sequence analysis software. If your next step is designing primers against the sequence, see how to use NCBI Primer-BLAST.
FAQ
How do I translate a DNA sequence to an amino acid sequence?
Paste the sequence into the “DNA or RNA sequence” box on Expasy Translate, choose the strand and genetic code, and read the amino acid sequence under “Results of translation”.
Does Expasy Translate accept RNA?
Yes. The input box is labelled “DNA or RNA sequence” and the tool is described as translating a nucleotide (DNA/RNA) sequence to a protein sequence.
Can Expasy Translate go from protein to DNA?
No. It translates nucleotide to protein only. Protein-to-DNA is reverse translation, which is a different task.
Which genetic code should I choose?
The one that matches the organism and compartment the sequence comes from. NCBI’s Table 1 (Standard) is the GenBank default for coding sequences; Table 2 is the vertebrate mitochondrial code.
What do the red regions in the results mean?
They are open reading frames. Select your initiator on the frame to retrieve that amino acid sequence.
Can I send the result to other tools?
Yes. The page offers direct submission to ProtParam, ProtScale, Compute pI/Mw, PeptideMass and PeptideCutter, and downloads as FASTA or text.
Sources (official documentation, read 2026-11-07)
- Expasy Translate: https://web.expasy.org/translate/
- Expasy terms of use (revised 2025-10-01): https://www.expasy.org/terms-of-use
- NCBI, The Genetic Codes (Elzanowski and Ostell, updated 2024-09-23): https://www.ncbi.nlm.nih.gov/Taxonomy/Utils/wprintgc.cgi
- NCBI ORFfinder: https://www.ncbi.nlm.nih.gov/orffinder/
- EMBOSS transeq: https://emboss.sourceforge.net/apps/release/6.6/emboss/apps/transeq.html
