How is this different from the regular Base64 Decoder?

The string category's Base64 Decoder treats your input as one Base64 string. This tool splits your input into list items first and decodes each one independently, which is what you need if the input is a list of encoded values, not one combined blob.

What happens if one item isn't valid Base64?

The tool stops and reports which item (by its position in the list) failed, rather than silently skipping it or corrupting the rest of the output.

Does whitespace around an item matter?

Each item is trimmed before decoding, so accidental leading/trailing whitespace won't cause a false failure.

How do I produce a Base64-encoded list to test with?

Use the companion List Base64 Encoder to Base64-encode a plain list, then decode it back here to confirm the round trip.

List Base64 Decoder - Decode Every List Item from Base64

Overview

Introduction

When you have a list of Base64-encoded values, exported IDs, tokens, or config values, decoding them one at a time by hand is slow and easy to get wrong if even one entry is malformed.

This tool decodes an entire list of Base64 items in one pass, catching and clearly reporting any single item that isn't valid rather than failing silently.

What Is List Base64 Decoder?

The List Base64 Decoder is a per-item decoder: it splits the input on your chosen separator and Base64-decodes each item independently back to UTF-8 text.

It's the exact inverse of the List Base64 Encoder, so a list encoded there decodes back here to the original values.

How List Base64 Decoder Works

The input is split into items on your chosen separator, trimmed, and blank items are dropped.

Each item is passed through the browser's native `atob()`, converted from a binary string back to bytes, and decoded as UTF-8 in strict mode; if `atob()` throws or the bytes aren't valid UTF-8, the error names that item's 1-based position and value.

When To Use List Base64 Decoder

Use this whenever you have a list of independently Base64-encoded values and need the plain text back, for example a batch of encoded tokens from a config file or export.

It's a better fit than the plain Base64 Decoder whenever your input is a list of separate encoded values rather than one combined Base64 blob.

Often used alongside List Base64 Encoder, Base64 Decoder and List URL Decoder.

Features

Advantages

Names the exact item that fails to decode, instead of a generic "invalid Base64" error for the whole input.
UTF-8 safe, so decoded text with accented characters or emoji comes back correctly.
Trims each item automatically, so incidental whitespace doesn't cause false failures.

Limitations

Stops at the first invalid item rather than decoding the valid ones and skipping the rest, since a corrupted list is likely worth fixing at the source.
Doesn't decode a single whole-text Base64 blob, use the plain Base64 Decoder for that case.

Examples

Decoding a valid list

Input

YWRtaW4=
ZWRpdG9y
dmlld2Vy

Output

admin
editor
viewer

Each Base64 string decodes independently back to its original plain-text role name.

Decoding a single item

Input

SGVsbG8sIFdvcmxkIQ==

Output

Hello, World!

A single-item list decodes to a single-item result, same as any other list length.

Best Practices & Notes

Best Practices

If decoding fails, check the reported item number first to find the malformed entry quickly in a long list.
Use the List Base64 Encoder to generate test data if you want to confirm the decoder round-trips correctly.

Developer Notes

Each item is decoded with the native `atob()`, converted to a `Uint8Array` via `Uint8Array.from(binary, char => char.charCodeAt(0))`, then decoded with `new TextDecoder("utf-8", { fatal: true })`; both a thrown `atob()` error and a UTF-8 decode failure are caught and reported with the failing item's position.

List Base64 Decoder Use Cases

Decoding a batch of Base64-encoded tokens exported from a config file or database
Validating that a list of encoded values is well-formed before importing it elsewhere
Round-tripping test data produced by the List Base64 Encoder

Common Mistakes

Pasting a single combined Base64 blob into this per-item decoder, it will likely fail or produce one nonsensical "item", use the plain Base64 Decoder instead for that case.
Assuming a failed decode means the whole list is unusable, only the reported item is invalid; the rest can still be decoded once it's fixed or removed.

Tips

URL-safe Base64 (using "-"/"_" instead of "+"/"/") needs converting back to standard Base64 characters before decoding here.
Keep an eye out for accidental double-encoding, if an "item" decodes to more Base64-looking text, it may have been encoded twice.

List Base64 Decoder