# Convert an Uint8Array to a base64 encoded string

Encode byte values as base64 with btoa.

Canonical: https://1loc.dev/string/convert-an-uint8-array-to-a-base64-encoded-string/
Version: 1.0.0
Runtime: JavaScript · Node.js 22 / modern browsers
Verification: Local fixtures; no external services
Updated: 2026-10-28

## Implementation

```javascript
function bytesToBase64(bytes) { return btoa(String.fromCharCode(...bytes)); }
```

## Input

```json
[
  72,
  101,
  108,
  108,
  111
]
```

## Expected output

```json
"SGVsbG8="
```

## Edge case

Input:
```json
[]
```
Output:
```json
""
```

## Limits

- Spreading is fine for the lab’s 1,000 bytes. For files, use Buffer.from(bytes).toString("base64") in Node.js or encode in chunks.
- This is the encoding Oveyon expects in an attachment’s content field.

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/convert-an-uint8-array-to-a-base64-encoded-string.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: Uses String.fromCharCode with spread instead of building an array of characters; bytes validated 0–255. Original MDX retained as inert source evidence.