Installing packages

Find a package, install it into libs/, and verify the archive you got. Downloads are public — no account and no token needed.

The standard library is not installed: it ships inside the compiler. Only packages you opt into live in the registry, and this page covers putting one in your project.

Find a package

Browse Libraries, where packages can be searched by name, keyword or summary and sorted by popularity, recency or name. Each package has its own page at /libraries/<name> listing every published version.

The same data is available to tooling:

bash

curl -s "https://sere-lang.com/api/packages?q=math&sort=downloads&limit=5"

q matches names, keywords and summaries. sort accepts:

Value	Order
`downloads`	Most downloaded first — the default
`recent`	Most recently published first
`name`	Alphabetical
`relevance`	Name matches ranked above keyword and summary matches

Install the latest version

bash

sere add mathlib

If your toolchain does not have sere add yet, download the archive and drop it into libs/ yourself:

bash

mkdir -p libs/mathlib
curl -Lo mathlib-0.1.0.tar.gz \
  "https://sere-lang.com/api/packages/mathlib/0.1.0/download?stream=1"
tar -xzf mathlib-0.1.0.tar.gz -C libs/mathlib

A packed .slib needs no extraction — copy the file straight into libs/. Then import it like any other library:

sere

import mathlib



def main() -> i32:

    return mathlib.add(2, 3)

Install a specific version

bash

sere add mathlib@0.1.0

Pinning an exact version is safe: a published version is immutable, so 0.1.0 always resolves to the same bytes and the same checksum. latest is the one that moves.

Where packages live

Path	What it is
`libs/mathlib/lib.sere`	A folder library — the entry file
`libs/mathlib.sere`	A single-file library
`libs/mathlib.slib`	A packed library
`libs/mathlib/native/`	Optional C sources, compiled with the library

Anything in libs/ is importable, whether it came from the registry or not. Removing a package means deleting it from libs/.

The download API

The registry serves downloads itself, so a client never needs to know where the files are stored.

Endpoint	Purpose
`GET /api/packages/mathlib/download`	The latest release
`GET /api/packages/mathlib/download?version=0.1.0`	Exactly that version
`GET /api/packages/mathlib/download?version=0.1`	The newest release starting with `0.1`
`GET /api/packages/mathlib/0.1.0/download`	The same thing, with the version in the path
`HEAD /api/packages/mathlib/0.1.0/download`	Size and checksum, without the archive

The version selector accepts:

Selector	Resolves to
omitted, `latest`, `*`	The highest release without a prerelease tag
`0.1.0`	Exactly that version
`0.1` or `0`	The highest release matching that prefix

Prereleases are deliberately skipped by latest and by partial selectors. To install one, name it exactly: ?version=0.2.0-rc.1.

Redirects, or the bytes themselves

By default a download answers 302 and sends you to the stored object, which keeps archives off the application server:

bash

curl -LO https://sere-lang.com/api/packages/mathlib/download

Add stream=1 to have the archive proxied through the API instead — useful when you want the file name and the checksum headers in the same response:

bash

curl -Lo mathlib-0.1.0.tar.gz \
  "https://sere-lang.com/api/packages/mathlib/0.1.0/download?stream=1"

Either way the response carries what you need to verify it:

Header	Meaning
`X-Package-Name`	Package name
`X-Package-Version`	The version that was resolved
`X-Checksum-Sha256`	SHA-256 of the archive, also sent as the `ETag`
`X-Package-Bytes`	Archive size in bytes

HEAD answers with the same headers without transferring the archive, and without counting a download. GET counts one.

Read metadata without downloading

bash

curl -s https://sere-lang.com/api/packages/mathlib
curl -s https://sere-lang.com/api/packages/mathlib/0.1.0

The first returns every published version with a download path for each, plus latestVersion and latestDownload. The second returns one version:

json

{
  "name": "mathlib",
  "version": "0.1.0",
  "summary": "Small numeric helpers.",
  "license": "MIT",
  "entry": "lib.sere",
  "bytes": 18421,
  "checksumSha256": "9f2c4d…e1",
  "publishedAt": "2026-09-18T10:12:04.512Z",
  "download": "/api/packages/mathlib/0.1.0/download",
  "downloadUrl": "https://…/packages/mathlib/0.1.0/mathlib-0.1.0.tar.gz",
  "install": "sere add mathlib@0.1.0"
}

download is the endpoint to use; downloadUrl is the underlying stored object, handy if you would rather fetch from the CDN directly.

Verify what you downloaded

Compare the SHA-256 of the file against the checksumSha256 the registry reports:

bash

sha256sum mathlib-0.1.0.tar.gz                    # Linux
shasum -a 256 mathlib-0.1.0.tar.gz                # macOS
Get-FileHash mathlib-0.1.0.tar.gz -Algorithm SHA256   # PowerShell

A mismatch means a truncated or altered download — delete it and fetch it again. Because a version can never change, a matched checksum is worth caching.

Updates

Ask for the current release without downloading anything:

bash

curl -s https://sere-lang.com/api/packages/mathlib/download \
  -o /dev/null -D - | grep -i x-package-version

Then pin whichever version you settle on. Resolving latest gives you the newest release; naming an exact version gives you a reproducible build, since the bytes behind it are fixed.

Troubleshooting

Response	Meaning	What to do
`404 No package named "x"`	The name is wrong, or nothing is published under it.	Search Libraries.
`404 … has no version matching "x"`	The package exists but no version matched the selector. The response lists the versions that do exist.	Pick one from the list.
`404 … has no published versions yet`	The package row exists with no release.	Ask the publisher to push a version.
`429`	More than 120 downloads in a minute from your network.	Wait for the `Retry-After` header, then retry.
`503`	The deployment cannot reach package storage.	This one is for the site's operator, not you.
Checksum mismatch	The archive was truncated or altered in transit.	Delete it and download again.

Limits and caching

Limit	Value
Downloads and metadata reads	120 per minute per network
Archive size	25 MB per version
Response caching	One year, `immutable` — versions cannot change
Versions	Immutable; a published version is never rebuilt

Next steps

Libraries — search the registry.
Publishing a package — put your own library in the registry.
Developer accounts — tokens and publishing from CI.