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

ORF Finder

You can find open reading frames in all six frames of a DNA or RNA sequence, with start and stop positions, amino acid length and the protein sequence for each ORF.

Runs in your browserFree · No sign-up · No watermark
DNA/RNA → ORFsRuns in your browser
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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 → ORFs
Processing
In your browser
Price
Free, no account
Updated
October 21, 2026
All Biology Tools

About ORF Finder

An open reading frame is a stretch of sequence between a start codon and an in-frame stop codon that could encode a protein. Scanning all six frames, three on each strand, is a standard first pass when a new sequence arrives and no annotation is available.

This ORF finder scans three forward and three reverse-complement frames, starts at ATG, ends at the first in-frame TAA, TAG or TGA, and reports positions, amino acid length and protein sequence for each hit. A minimum length filter reduces noise, incomplete ORFs can be shown, and the proteins can be copied or downloaded as FASTA.

What this tool does

The details that matter when you use ORF Finder for real work.

  • All six frames

    Three forward frames and three reverse-complement frames are scanned, so ORFs on both strands are reported.

  • Start and stop positions

    Every ORF lists its 1-based start and end coordinates on the original sequence, its frame and its start and stop codons.

  • Amino acid length filter

    Set a minimum ORF length in amino acids, with 30 as the default, to hide very short readings.

  • Incomplete ORFs optional

    Enable incomplete ORFs to see ATG starts that reach the end of the sequence without an in-frame stop.

  • Protein display and copy

    Each row shows a truncated protein sequence with a copy button for the full sequence, sorted longest first.

  • FASTA copy and download

    Copy or download every listed ORF protein as FASTA with strand, frame, positions and stop codon in the header.

How to use ORF Finder

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

    Paste the sequence

    Paste DNA or RNA, raw or in a FASTA record; RNA is converted to DNA and formatting is removed.

  2. 02

    Set the minimum length

    Enter the shortest ORF, in amino acids, that should be reported; the default of 30 removes many short chance ORFs.

  3. 03

    Decide about incomplete ORFs

    Leave the checkbox off for complete ORFs only, or enable it to include starts without an in-frame stop.

  4. 04

    Review the sorted list

    ORFs are sorted by amino acid length; check strand, frame, positions and start and stop codons for each one.

  5. 05

    Copy or download the proteins

    Copy a single protein, or copy or download all listed proteins as FASTA for further analysis.

How this tool works

Works with
DNA/RNA → ORFs
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 with ATG as the only start codon, and does not model alternative starts, mitochondrial codes, introns, splicing or sequencing errors.
  • Every ATG is reported independently, so nested ORFs can appear and the list is not a gene prediction.
  • Ambiguous codons translate to X and cannot act as start or stop signals, so a start or stop hidden behind an unknown base is not detected.

Privacy and file handling

The sequence you paste stays in this browser tab. Six-frame scanning, translation and FASTA generation run with JavaScript on your device, so nothing is uploaded, stored or logged, and closing the page discards the input.

Read the full privacy policy

ORF Finder FAQ

Short, direct answers to the questions people ask before using this tool.
What counts as an open reading frame here?
An ORF starts at an ATG codon and ends at the first in-frame TAA, TAG or TGA codon, so it contains a start and a stop in the same frame. The amino acid length counts the start codon and excludes the stop.
Why scan six frames instead of one?
A DNA sequence can encode proteins on either strand, and each strand has three possible reading frames. Scanning all six covers the forward strand and the reverse complement, so an ORF is not missed simply because it lies on the opposite strand.
How are positions on the reverse strand reported?
Positions are always given as 1-based coordinates on the original sequence with start below end. For a reverse-strand ORF the reported start is the lower coordinate, even though transcription on that strand runs in the opposite direction.
Why are there so many ORFs in a random sequence?
A stop codon occurs roughly every 21 codons by chance, and ATG appears often, so short random ORFs are expected. Raising the minimum length or requiring a complete ORF removes most of them, but the list is still not a gene prediction.
What does an incomplete ORF mean?
It is an ATG start with no in-frame stop codon before the end of the sequence, so it may be a genuine ORF that is truncated in the input or simply a chance start. Incomplete ORFs are hidden by default and can be shown with the checkbox.
How are ambiguous codons handled in ORF finding?
Codons containing N or another ambiguity code translate to X and are never treated as start or stop codons. A hidden ATG or stop codon behind an ambiguous base therefore cannot be detected, and the tool warns when ambiguity codes are present.
Does the ORF finder use the standard genetic code?
Yes, it uses the standard code with ATG as the only start and TAA, TAG and TGA as stops. Alternative start codons, mitochondrial codes, introns, splicing and sequencing errors are not modeled.
Is my sequence uploaded anywhere?
No. Six-frame scanning, translation and FASTA generation 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 ORF Finder.