# Encode a URL component strictly

Percent-encode a value, including !'()* that encodeURIComponent leaves alone.

Canonical: https://1loc.dev/misc/encode-a-url/
Version: 1.0.0
Runtime: JavaScript · Node.js 22 / modern browsers
Verification: Local fixtures; no external services
Updated: 2026-10-28

## Implementation

```javascript
function encodeStrict(value) { return encodeURIComponent(value).replace(/[!'()*]/g, char => `%${char.charCodeAt(0).toString(16).toUpperCase()}`); }
```

## Input

```json
"it's (50%) off!"
```

## Expected output

```json
"it%27s%20%2850%25%29%20off%21"
```

## Edge case

Input:
```json
"~-_."
```
Output:
```json
"~-_."
```

## Limits

- RFC 3986 unreserved characters (- _ . ~) stay as they are, as the edge case shows. The original also encoded ~, which RFC 3986 leaves unreserved.

The lab validates types and size before calling this function. Add equivalent validation at your own trust boundary.

## Source and license

Original: https://github.com/phuocng/1loc/blob/14b481cf60dff1620ab1bb99a43b1f68068cdd9b/contents/encode-a-url.mdx
Author: Nguyen Huu Phuoc and original contributors
Contributors: See original repository history
Source commit: 14b481cf60dff1620ab1bb99a43b1f68068cdd9b
Copyright (c) 2020 phuoc-ng
License: MIT — https://1loc.dev/licenses/
Maintainer: Oveyon
Modifications: Encodes !'()* with one replacement and leaves RFC 3986 unreserved ~ as is. Original MDX retained as inert source evidence.