SnapGene .dna File Viewer — Open a .dna in Your Browser
Open a SnapGene .dna file and read its sequence, features, colours and primers — no SnapGene, no account.
🔒 Nothing you paste is logged or stored
A colleague sends you a plasmid as a .dna file and nothing you have installed will open it. SnapGene's format is a binary container that has never been publicly specified, so a text editor shows garbage and renaming the file does not help. Drop the file here and SeqBench decodes it with its own reader: the full sequence, whether the construct is circular, every feature with its type, span, strand, saved display colour and free-form qualifiers — including spliced features and features that wrap the origin — and the primers stored inside the file. Export the whole record as GenBank, or the sequence alone as FASTA. The file is read in this browser tab and is not uploaded.
Working on a whole construct rather than a quick look? Open SeqStudio — the full editor, with live feature annotation, plasmid maps, restriction and primer panels, undo/redo, multi-document tabs and GenBank / SnapGene import and export.
How to use the SnapGene Viewer tool
- 1Drop a SnapGene .dna file onto the box, or click to choose one. The bytes are checked for the "SnapGene" signature first, so a mislabelled GenBank, FASTA or .ab1 is named for what it is and pointed at the page that opens it, rather than failing with a wall of garbage.
- 2Read the summary line — length, topology, feature and primer counts — then use the View dropdown to switch between the circular and linear maps. The map opens on whichever topology the file declares.
- 3Scan the Features table for each label, type, location, strand and length, and click a row to see its qualifiers. Origin-spanning and spliced features are marked as such rather than being flattened into one span.
- 4Download the record as GenBank, the sequence as FASTA, or the map as SVG/PNG/PDF — or open the file in SeqStudio if you need to edit it and write a .dna back out.
Frequently asked questions
Do I need SnapGene installed to open a .dna file?
No. SeqBench reads the .dna format directly. SnapGene has never published a specification, so every reader outside SnapGene itself — Biopython's SnapGeneIO, Edinburgh Genome Foundry's snapgene-reader, and this one — is reverse-engineered from the file's segment structure: a one-byte type, a four-byte big-endian length, then the payload, with features and primers held as XML inside the binary wrapper.
What does it read out of the file?
The sequence and its topology (circular or linear), every feature with its label, type, 1-based span, strand, saved display colour and its full qualifier bag (/gene, /product, /note, /translation and anything else the file carries), and the primer list with names and sequences. Spliced features keep their separate parts instead of being collapsed into one enclosing span, and a feature crossing the origin of a circular plasmid is read as the descending span it is, then drawn as the two arcs it really is — not as a feature covering the whole plasmid.
Are there .dna files this cannot open?
One kind: SnapGene can store its sequence compressed, and this reader cannot decompress that form. It says so explicitly rather than reporting an empty file — re-export from SnapGene as an uncompressed .dna, or as GenBank, and it opens. Two smaller caveats worth knowing: an .xdna file is SnapGene's XML export and a different format, and non-ASCII characters in feature labels are not decoded faithfully, so a label containing a Greek letter may come back garbled.
Can I convert a .dna to GenBank?
Yes — that is usually why people need the file open at all. The GenBank export carries the sequence, topology, features, their qualifiers, their reading frame and spliced join() locations. It does not carry the primers, because GenBank has no primer channel; they are listed on the page so you can copy them.
Can I edit the file and save it back as .dna?
Not on this page — this is a viewer. Open the same file in SeqStudio, SeqBench's editor: it reads .dna, remaps features live as you edit, and writes .dna back out, keeping the segments this reader does not model byte-identical so that a colleague's file does not come back poorer than it went in.
Is my file uploaded or stored?
No. The .dna is decoded in this browser tab to produce the sequence, features and primers, and is never uploaded, logged or stored. The same parsing is also available server-side through the REST API and the MCP server if you want to script it.
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