sveltejs/svelte

By the numbers

Active contributors: Rich Harris, Simon H, Dominic Gannaway

Data collected on 2026-04-30 from commit 572444a69.

Size

Metric	Lines
Source JavaScript (`packages/svelte/src/*/.js`, no tests)	62,334
Source TypeScript declarations (`.ts`, `.d.ts`)	3,744
Co-located unit tests (`src/*/.test.*`)	2,304
Vitest test corpus under `packages/svelte/tests/`	74,522
Total (`.js` + `.ts` source + tests)	142,904

There are 410 source files under packages/svelte/src/ and exactly one published package, svelte. The repo is a pnpm workspace with packages/* (one entry) and playgrounds/* declared in pnpm-workspace.yaml.

Language breakdown (source only, excluding tests)

xychart-beta horizontal
    title "Lines of code by language (packages/svelte/src/)"
    x-axis [JavaScript, TypeScript]
    y-axis "Lines" 0 --> 65000
    bar [62334, 3744]

The Svelte source is intentionally JavaScript-first — TypeScript is used only for .d.ts declarations and a handful of internal type-helper files. The tests directory is a different mix (most tests are in .test.ts).

Single-file complexity

Largest source files (all under packages/svelte/):

File	Lines
`src/compiler/phases/1-parse/utils/entities.js`	2,234
`src/compiler/migrate/index.js`	1,998
`src/compiler/errors.js` (generated)	1,718
`src/compiler/phases/scope.js`	1,471
`src/compiler/phases/2-analyze/index.js`	1,325
`src/internal/client/reactivity/batch.js`	1,280
`src/compiler/phases/2-analyze/css/css-prune.js`	1,247
`src/internal/server/renderer.js`	945
`src/compiler/phases/1-parse/state/element.js`	950
`src/compiler/warnings.js` (generated)	844
`src/internal/client/runtime.js`	837

The biggest single file is the HTML entities table (entities.js) — pure data. The biggest hand-authored file is the Svelte 4 → 5 migration codemod.

Activity

Window	Commits
Last 30 days	47
Last 90 days	258
All-time	11,150

The repo's first commit is fc7e6e6 from 2016-11-15.

xychart-beta horizontal
    title "Commits per year"
    x-axis [2016, 2017, 2018, 2019, 2020, 2021, 2022, 2023, 2024, 2025, 2026]
    y-axis "Commits" 0 --> 2500
    bar [408, 1558, 1288, 2280, 520, 517, 355, 860, 2054, 955, 355]

The 2024 spike corresponds to the Svelte 5 push (the 5.0.0 tag landed 2024-10-19). The lower 2020-2022 numbers reflect the Svelte-3-mature, Svelte-4-incremental period.

Churn hotspots (last 90 days)

Files modified most often in the last 90 days:

File	Touches
`packages/svelte/package.json`	41
`packages/svelte/CHANGELOG.md`	35
`packages/svelte/src/version.js`	34
`packages/svelte/src/internal/client/reactivity/batch.js`	34
`packages/svelte/src/internal/client/reactivity/deriveds.js`	16
`packages/svelte/src/internal/server/renderer.js`	12
`packages/svelte/src/internal/client/reactivity/effects.js`	12
`packages/svelte/src/internal/client/reactivity/async.js`	11
`packages/svelte/src/internal/client/dom/blocks/boundary.js`	9

package.json, CHANGELOG.md, and version.js churn is dominated by changesets-driven release commits. The reactivity scheduler (batch.js) is the most-modified hand-authored file — consistent with it being the most-watched correctness target in Svelte 5.

Bot-attributed commits

675 / 11,150 commits (~6.1%) carry an explicit Co-authored-by: ...[bot] trailer. This is a lower bound on AI/bot involvement — inline tools like Copilot and Cursor don't leave a trace. The most common bot is changeset-bot, which authors the release-prep commits.

Contributors

Top contributors over the package's full history (excluding [bot] accounts), based on commit count:

Author	Commits
Rich Harris	3,983 (across the `Rich Harris` and `Rich-Harris` aliases — and a small number under `Richard Harris`)
Conduitry	804
Simon H	696
Dominic Gannaway	497
Tan Li Hau	320
Ben McCann	246
Paolo Ricciuti	245
Puru Vijay	118

There are 921 unique commit authors all-time. The bus factor on the core reactivity engine is low (Rich, Dominic, Simon are the top three by edits to internal/client/reactivity/).

Dependencies

packages/svelte/package.json declares:

16 runtime dependencies (notable: acorn, magic-string, esrap, zimmerframe, clsx, devalue, aria-query, axobject-query).
15 devDependencies (Rollup, Vitest, Playwright, esbuild, dts-buddy, etc.).

The top-level package.json adds 16 more devDependencies for the monorepo (changesets, eslint configs, prettier, vitest coverage).