How to fly the pixelverse
Every pixel is one base of the human reference genome (GRCh38): A C G T , pale where the base is in a repeat, near-black where it isn't known (N). Zoomed out, a pixel is the average colour of the bases it covers. Rows wrap like lines of text.
scroll / drag move along the chromosome ctrl + scroll, pinch, + − zoom double-click zoom in there (shift: out) shift + drag select bases click a gene highlight it / or G search K karyotype R random gene 1 2 3 gene, one transcript, every transcript (expanded) [ ] previous / next gene P save a picture Esc clear
Search for genes (symbols, old names, Ensembl IDs), places (chr7:117,480,025-117,668,665, X:73.8M), bands (17q21.31) or variants (rs334).
What you are looking at
This is a browser for gpxil , a file format that stores genomes as images, after Guenter Albrecht-Buehler's genome pixel images (PLoS ONE, 2009 ). The bases come straight from the GRCh38 gpxil files: the browser reads just the strips of pixels it needs with HTTP range requests.
Only when you ask for them, a few things come live from other databases: variants, regulatory elements, rsID lookups and names the gene index doesn't know from the Ensembl REST API , and gene summaries from NCBI Gene via MyGene.info .
© 2026 Chronomic Medicine Group, Department of Genomic Medicine, University of Cambridge. The Gpxil browser is free software under the MIT licence ; its code is at github.com/comparativechrono/Gpxil-browser .
Take the pixels home
The genome as gpxil
The whole GRCh38 reference in one gpxil file, GRCh38.gpxil.tif (about 850 MB; SHA-256 ), or a chromosome at a time: these are the files this browser reads.
From the command line:
curl -LO https://github.com/comparativechrono/Gpxil-browser/releases/download/grch38-ensembl116/GRCh38.gpxil.tif Copy To check it, download the SHA-256 file beside it and run sha256sum -c GRCh38.gpxil.tif.sha256 (on a Mac, shasum -a 256 -c GRCh38.gpxil.tif.sha256). If the download stops, the same command with -C - after curl carries on from where it stopped.
Read them with gpxiltools (pip install git+https://github.com/comparativechrono/Gpxil-tools, then gpxil info chr17.gpxil.tif), or open them in any TIFF viewer.
Genes, transcripts and proteins as pxil
Open a gene and use Download as pixels in its panel: .gene.pxil.png, .transcript.pxil.png and .protein.pxil.png files, one at a time or zipped, each named with its Ensembl ID. pxil is a simple format for single sequences: PNG images that open in any image viewer and whose pixel values are the sequence. It is good for quick analysis and sharing, while gpxil is for keeping genomes.
The formats
© 2026 Chronomic Medicine Group, Department of Genomic Medicine, University of Cambridge · MIT licence