UK Public Sector GitHub Observatory
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
customs-declarations-end-to-end-service-guideWhat stands out
customs-declarations-end-to-end-service-guide is 3.0 GB of git - a 2013 static snapshot of www.gov.uk, not source code. It single-handedly makes HTML the largest language by volume (8% of all source bytes). Any size or language statistic that does not exclude it is measuring an archive, not a codebase.
This organisation was harvested with blobless partial clones, which fetch every commit and file path but not file contents, so there is no local size to measure against. Checked elsewhere in this dataset against 1,526 fully mirrored repositories, GitHub's reported size is accurate to within about six percent.
Ruby is the primary language of 2% of archived repositories but only 0% 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.
70% 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 |
|---|---|---|---|---|---|
| customs-declarations-end-to-end-service-guide | Batchfile | 3.0 GB | 788 | 62 | active |
| datahub | Java | 409.5 MB | 9,136 | 4,340 | active |
| hmrc-screens | JavaScript | 168.0 MB | 387 | 1,983 | active |
| goods-survey | CSS | 159.8 MB | 38 | 111 | active |
| vault | Go | 137.5 MB | 17,297 | 12,581 | archived |
| cds-reimbursement-claim-ui-tests | Scala | 131.8 MB | 1,485 | 315 | active |
| excise-movement-control-system-api-tis | HTML | 116.3 MB | 183 | 491 | active |
| help-to-save-frontend | Scala | 110.5 MB | 4,050 | 225 | active |
| upscan-performance-tests | Scala | 107.9 MB | 118 | 24 | active |
| service-manager | Python | 100.8 MB | 556 | 125 | archived |
| upload-customs-documents-performance-tests | Scala | 84.8 MB | 30 | 34 | active |
| pension-administrator-frontend | Scala | 76.9 MB | 4,529 | 1,333 | active |
| fset-faststream-frontend | Scala | 67.3 MB | 2,449 | 672 | active |
| tai-frontend | Scala | 64.7 MB | 6,955 | 991 | active |
| customs-declarations | Scala | 57.4 MB | 1,772 | 4,501 | active |
| hmrc-frontend | JavaScript | 55.9 MB | 1,743 | 595 | active |
| pension-scheme-accounting-for-tax-frontend | Scala | 55.8 MB | 4,737 | 1,091 | active |
| mtd-sa-test-support-api | Scala | 54.8 MB | 447 | 361 | active |
| push-pull-notifications-acceptance-tests | Java | 51.6 MB | 303 | 54 | active |
| android-components | Kotlin | 51.1 MB | 1,243 | 607 | active |