HomeBlogWhat happened to our package sizes between 2.2.6 and 5.0.1

What happened to our package sizes between 2.2.6 and 5.0.1

October 10, 2026

Between 2.2.6 (2026-09-21) and 5.0.1 (2026-10-10) the six published packages went from about 7.44 MB to about 5.94 MB unpacked. That is the headline number, and it is a little misleading: three of the six packages got bigger. This post lists the measured numbers for every package and explains the two changes behind most of the savings.

How these numbers were taken

For each package I ran npm pack --dry-run --json <name>@<version> against the npm registry from a scratch directory, outside the repo, and read size (the packed tarball, which is what a download costs) and unpackedSize (what lands in node_modules). I did not install anything. Two earlier figures in circulation, from an internal report, were unpacked-only and did not include packed sizes; the packed column below is new.

I'm not reporting gzip numbers from our README badges. Those badges changed definition in this window (they now include dependencies), so an old badge and a new badge don't measure the same thing.

The numbers

Package Packed 2.2.6 Packed 5.0.1 Unpacked 2.2.6 Unpacked 5.0.1 Files
zombie-mermaid 309,513 24,148 1,253,846 74,590 109 → 16
@zombie-mermaid/core 227,901 142,952 618,569 435,761 28 → 8
@zombie-mermaid/mermaid-parser 150,164 199,747 499,820 669,228 26 → 8
@zombie-mermaid/svg-renderer 383,658 510,232 1,468,214 1,818,151 34 → 9
@zombie-mermaid/ascii-renderer 869,978 770,064 3,244,612 2,819,450 233 → 9
@zombie-mermaid/mcp 96,977 25,222 355,020 120,447 17 → 8
Sum 2,038,191 1,672,365 7,440,081 5,937,627

All sizes are bytes. The sum is about 18% smaller packed and about 20% smaller unpacked.

One caveat on the sum: zombie-mermaid is a thin wrapper that depends on the other five at the exact same version, so installing it pulls in all of them. The umbrella package shrinking by 94% unpacked does not make an install 94% smaller. The column that matches what an install costs for the umbrella is the sum.

Cause 1: src/ is no longer published

In 2.2.6 the tarballs shipped both dist/ and a copy of src/. Breaking the 2.2.6 contents down by top-level directory:

  • zombie-mermaid: 966,469 of 1,253,846 unpacked bytes were src/ (77%), and 263,323 were dist/.
  • @zombie-mermaid/ascii-renderer: 1,234,877 of 3,244,612 unpacked bytes were src/ (38%), with 2,005,782 in dist/.

In 5.0.1 the umbrella and ascii-renderer contain no src/ at all, which is where most of the file-count drop comes from (233 files down to 9 for ascii-renderer). This came from #1446, "drop duplicated src from tarballs, remove unused deps", which merged as part of 5.0.0. mcp dropping from 355,020 to 120,447 unpacked bytes fits the same pattern, though I only broke down the umbrella and ascii-renderer by directory.

Cause 2: elkjs is an optional peer dependency

elkjs is the ELK layout engine, and it is large: the registry reports 8,137,099 unpacked bytes for elkjs@0.11.0. In 2.2.6, @zombie-mermaid/core listed it as a regular dependency, so every consumer got it, including people who only wanted ASCII output.

In 5.0.1, per the registry manifests:

  • @zombie-mermaid/core has no dependencies.
  • @zombie-mermaid/ascii-renderer depends only on core and mermaid-parser.
  • @zombie-mermaid/svg-renderer declares elkjs as an optional peer dependency (peerDependenciesMeta.elkjs.optional: true).

This is #1444, a breaking change in 5.0.0 that adds registerElk() so you hand the renderer your own ELK instance. The tradeoff is that browser and bundler apps now have to call it once:

import ELK from 'elkjs/lib/elk.bundled.js'
import { registerElk } from 'zombie-mermaid'

registerElk(ELK)

The savings here don't show up in the table, because npm pack measures only the package's own files, not what it pulls in. They show up in node_modules: an ASCII-only install of @zombie-mermaid/ascii-renderer no longer brings in the elkjs tree at all. I did not install the packages to measure the resulting node_modules size, so I'm not putting a number on that.

One thing worth stating plainly: the umbrella zombie-mermaid@5.0.1 still lists elkjs as a regular dependency, so installing the umbrella still installs it. The opt-out applies to the standalone packages.

Why three packages got bigger

@zombie-mermaid/mermaid-parser grew about 34% unpacked (499,820 to 669,228) and @zombie-mermaid/svg-renderer about 24% (1,468,214 to 1,818,151). Both packages gained code in this window; the internal report this post was drafted from puts source growth at roughly 3.7k to 8.2k TypeScript lines for the parser and 9.5k to 17.2k for the SVG renderer. I haven't broken those increases down by feature, so I won't claim which diagram types account for what.

@zombie-mermaid/ascii-renderer is the interesting one: it lost its src/ copy and still only fell about 13% unpacked (3,244,612 to 2,819,450), because its dist/ grew to absorb the savings. Its TypeScript source reportedly grew from about 31k to 47k lines over the same period.

What we're not claiming

  • Bundle size in your app depends on your bundler and what you import. These numbers are package sizes on npm, not bundle sizes.
  • The comparison is exactly two versions. I did not measure the versions in between, so I can't say which release each change landed in beyond what the linked issues say.
  • Runtime speed was not part of this measurement.