Sanger Trace Viewer — Open & View .ab1 Chromatograms Online
View an .ab1 / .abi Sanger chromatogram, read the base calls and export the trace.
🔒 Local processing — pasted sequences are not uploaded
Upload a Sanger sequencing trace (.ab1 / .abi) and read the chromatogram directly in your browser. The Sanger Trace Viewer parses the raw ABIF file and draws the four processed dye channels as an electropherogram — G black, A green, C blue, T red — with the called bases positioned over their peaks. It reports the read length and mean Phred quality, lets you copy or download the base calls as FASTA, and exports the trace figure as SVG or PNG. Nothing is uploaded: the whole file is decoded on your device.
Your chromatogram is parsed locally in your browser — nothing is uploaded.
The viewer decodes the raw ABIF (.ab1 / .abi) chromatogram: the four processed dye channels are drawn as an electropherogram (G black, A green, C blue, T red) with the called bases positioned over their peaks. Read length and mean Phred quality summarise the read; export the base calls as FASTA or the trace as an SVG/PNG figure. Low peaks, broad or overlapping peaks, and stretches of low quality near the ends are the usual signs to trim before downstream analysis.
How to use the Sanger Trace Viewer tool
- 1Upload your Sanger trace file (.ab1 or .abi) from your sequencer.
- 2Scroll the electropherogram to inspect peak shape and the base calls above each peak.
- 3Check the read length and mean quality, then export the base calls as FASTA or the trace as SVG/PNG.
Frequently asked questions
- Which file formats can I open?
- ABIF traces from Sanger sequencers — files with an .ab1 or .abi extension. The viewer parses the raw big-endian ABIF directory to extract the base calls (PBAS), per-base quality (PCON), the four processed trace channels (DATA9–12 mapped by FWO_) and the peak locations (PLOC). SCF is not decoded; convert it to .ab1 first.
- Is my trace file uploaded to a server?
- No. The .ab1 file is read and decoded entirely in your browser with the File API, so the chromatogram never leaves your device.
- What do the channel colors mean?
- The four dye channels use the classic ABI palette: G is black, A is green, C is blue and T is red. The channel order is read from the file's FWO_ tag, so channels are always mapped to the correct base.
- Can I export the read or the figure?
- Yes. Copy or download the base calls as a FASTA record, and export the electropherogram as a vector SVG or a high-resolution PNG for your notebook or a figure.
- How do I judge read quality?
- The viewer shows the read length and mean Phred quality. Clean single peaks and high quality indicate a reliable read; low, broad or overlapping peaks and low-quality stretches (usually near the ends) are the regions to trim before downstream analysis.