# Is ecdsa-sig-formatter ESM-only? Can you require() it?

> ecdsa-sig-formatter@1.0.11 is a CommonJS package. CommonJS — require() works on every Node.js version we test.

Translate ECDSA signatures between ASN.1/DER and JOSE-style concatenation

Last verified Sep 9, 2026 against ecdsa-sig-formatter@1.0.11.

ecdsa-sig-formatter ships CommonJS only. require("ecdsa-sig-formatter") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. import "ecdsa-sig-formatter" also works because Node.js and Bun can import CommonJS from ES modules, but only the default export is guaranteed; named imports depend on Node's static analysis of the module.

## What to do

1. require("ecdsa-sig-formatter") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun.
2. From ES modules use the default import: import ecdsaSigFormatter from "ecdsa-sig-formatter"; then destructure. Named imports only work when Node.js can statically detect the exports.
3. TypeScript: types are bundled; install nothing extra.

## Facts

- Latest: 1.0.11 (Jan 25, 2019)
- Module format: CommonJS
- Last CommonJS version: 1.0.11
- TypeScript types: bundled
- Node engines: not declared
- Weekly downloads: 39.1M
- License: Apache-2.0

## Runtime test results for ecdsa-sig-formatter@1.0.11

Installed and executed on Sep 9, 2026 with require("ecdsa-sig-formatter") from a CommonJS file and import "ecdsa-sig-formatter" from an ES module.

| Runtime | require("ecdsa-sig-formatter") | import "ecdsa-sig-formatter" |
|---|---|---|
| Node.js 18 | works | works |
| Node.js 20 | works | works |
| Node.js 22 | works | works |
| Node.js 24 | works | works |
| Node.js 26 | works | works |
| Bun 1.4.0 | works | works |

## How to import ecdsa-sig-formatter

ES modules:

```js
import ecdsaSigFormatter from "ecdsa-sig-formatter";
```

CommonJS:

```js
const ecdsaSigFormatter = require("ecdsa-sig-formatter");
```

## Module format by version

Derived from the type, main and exports fields of every stable release on npm (10 versions; the newest 10 shown).

| Versions | Format | First published |
|---|---|---|
| 1.0.0 – 1.0.11 | CommonJS | Jun 10, 2015 |

## Frequently asked

**Is ecdsa-sig-formatter ESM-only?**

ecdsa-sig-formatter@1.0.11 is a CommonJS package. ecdsa-sig-formatter ships CommonJS only. require("ecdsa-sig-formatter") works on every Node.js version we test (18, 20, 22, 24 and 26) and in Bun. import "ecdsa-sig-formatter" also works because Node.js and Bun can import CommonJS from ES modules, but only the default export is guaranteed; named imports depend on Node's static analysis of the module.

**Can I import ecdsa-sig-formatter with ES module syntax?**

Yes. import ecdsaSigFormatter from "ecdsa-sig-formatter" works in Node.js and Bun because they support importing CommonJS modules. Named imports work only when Node.js can statically detect the exports.

**Does ecdsa-sig-formatter work in Bun?**

Yes. import "ecdsa-sig-formatter" loaded successfully in Bun 1.4.0 on Sep 9, 2026.

**Does ecdsa-sig-formatter ship TypeScript types?**

Yes. ecdsa-sig-formatter bundles its own type declarations; no @types package is needed.

## Links

- [ecdsa-sig-formatter on npm](https://www.npmjs.com/package/ecdsa-sig-formatter)
- [Source repository](https://github.com/Brightspace/node-ecdsa-sig-formatter)
- [HTML version](https://canirequire.com/package/ecdsa-sig-formatter/)
- [JSON version](https://canirequire.com/package/ecdsa-sig-formatter.json)

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