Language figures come from GitHub's own per-repository byte counts, which measure source rather than a single headline label. File counts and repository sizes come from the mirrors themselves. The two tell different stories, and the difference is the point.
The codebase
govuk-archiveWhat stands out
govuk-archive is 8.7 GB of git - a 2013 static snapshot of www.gov.uk, not source code. It single-handedly makes HTML the largest language by volume (37% of all source bytes). Any size or language statistic that does not exclude it is measuring an archive, not a codebase.
Sizes on this page are measured from the mirrors rather than taken from the API, which allows the two to be compared across 1,526 repositories. They agree closely: the median mirror is 1.06× the reported size, and the totals are 12.1 GB reported against 13.0 GB on disk. Mirrors run marginally larger because they carry every ref and tag. Anyone planning a bulk clone can size it from the API and add ten percent.
Ruby is the primary language of 33% of archived repositories but only 25% of live ones. Python, Go, TypeScript and HCL have taken the difference - the signature of a shift from monolithic Rails publishing apps toward data pipelines, infrastructure-as-code and platform tooling.
65% of repositories are under a megabyte of git data. The estate is not a monolith - it is a very long tail of small services, gems and prototypes around a few large publishing applications.
Languages, two ways
By volume of source
Bytes of code. Dominated by archived static HTML.
By number of repositories
How many repositories name each language as their primary one. A better guide to what engineers actually work in.
Live estate versus archive
The same language ranking, split by whether the repository is still active. The shift is the clearest signal of technical direction in the whole dataset.
Active repositories
Archived repositories
Scale
Repository size distribution
Git data per repository, log-ish buckets.
Commits against files
Each circle is a repository, sized by number of distinct authors. Both axes are logarithmic. The diagonal band is the normal relationship between codebase size and churn; outliers above it are long-lived apps with heavy iteration, below it are dumps and imports.
The shape of a repository
Directory layout is the cheapest reliable signal of what a repository actually is.
app/ with config/ and spec/ is a Rails application;
src/ with test/ is Java or Node. Counted by how many repositories
contain each top-level directory at HEAD.
Most common top-level directories
Most common file extensions
By total file count across the estate.
The twenty largest repositories
| Repository | Language | Git size | Commits | Files | Status |
|---|---|---|---|---|---|
| govuk-archive | - | 8.7 GB | 0 | 0 | archived |
| kubernetes | Go | 649.7 MB | 88,683 | 19,269 | archived |
| assets-directgov | HTML | 498.4 MB | 61 | 3,998 | archived |
| emergency-alerts-admin | Python | 484.4 MB | 16,695 | 620 | active |
| govuk-lda-tagger | Jupyter Notebook | 428.2 MB | 173 | 132 | archived |
| govuk-topic-taxonomy-static-suggestions-experiment | HTML | 345.3 MB | 33 | 104,286 | active |
| notifications-admin | Python | 316.9 MB | 24,844 | 1,050 | active |
| govuk-topic-taxonomy-dynamic-suggestions-experiment | HTML | 293.6 MB | 85 | 52,221 | active |
| govuk-personalisation-showcase-2022 | HTML | 239.5 MB | 621 | 2,275 | archived |
| assets-businesslink | CSS | 239.1 MB | 30 | 6,927 | archived |
| whitehall | Ruby | 237.4 MB | 45,412 | 2,684 | active |
| tagging-suggester | Python | 234.9 MB | 49 | 635 | archived |
| govuk-helm-charts | Go Template | 215.4 MB | 248,719 | 721 | active |
| govuk-frontend | JavaScript | 206.5 MB | 20,540 | 1,040 | active |
| ckan | Python | 202.5 MB | 28,813 | 2,326 | archived |
| govdesign | - | 184.7 MB | 83 | 73 | active |
| ckan-fix | - | 181.0 MB | 28,176 | 2,855 | active |
| pay-products-ui | JavaScript | 166.0 MB | 6,102 | 169 | active |
| verify-event-store-schema | Shell | 158.9 MB | 13 | 10 | archived |
| datagovuk-visual-regression-tests | JavaScript | 148.2 MB | 126 | 403 | archived |