Bulk Base64 Decoder - Decode Multiple Lines

How to Use

1. Paste your Base64 lines into the input box above (one per row), or click "Sample".
2. Select Strict Mode or Auto-Detect Data URI below the input box to set batch rules.
3. Click "Decode" to convert all rows at once and view the batch summary count.
4. Use the "Copy" or "Download" buttons above the result box to get your decoded list.

Options Explained

• Strict Mode: Require exact Base64 syntax and valid UTF-8 or UTF-16 bytes, marking bad rows as [Invalid Base64].
• Auto-Detect Data URI: Strip text Data URI headers (like data:text/plain;base64,) on each row and reject binary formats (enabled by default).

Key Features

• Decode bulk lists of up to 100,000 Base64 lines at once with live line counting.
• Keep 1:1 row alignment by preserving blank rows and replacing decoded line breaks with spaces.
• Isolate errors per row with [Invalid Base64] labels without stopping the rest of the batch.
• Normalize URL-safe Base64 characters (- and _) and fix missing = padding on every row.
• Extract plain text, JSON, XML, SVG, CSV, and YAML from Data URIs while blocking binary rows.
• Decode UTF-8 and UTF-16 (LE/BE) byte streams locally in your browser with zero server storage.

About This Online Bulk Base64 Decoder

This bulk Base64 decoder processes up to 100,000 Base64 lines into plain text inside your browser. It decodes each row independently, fixes missing padding, and flattens internal line breaks to keep 1:1 spreadsheet alignment.

Developed and maintained by the PU Tools team, this tool gives you fast, accurate, safe, and easy results in just a few clicks.

Common Use Cases

• Server Log Analysis: Decode thousands of Base64-encoded log entries, webhook events, or tracking strings line by line.
• Spreadsheet Data Cleaning: Convert an entire column of Base64 strings from spreadsheets while keeping exact row alignment.
• Batch Data URI Extraction: Extract plain text, JSON objects, or SVG code from lists of Data URI strings.

Example Input and Output

Example Input

SGVsbG8gV29ybGQh
SGVsbG8tV29ybGQ_

data:text/plain;base64,V2VsY29tZSB0byBQVSBUb29scyE=

Options used: Strict Mode: OFF | Auto-Detect Data URI: ON

Example Output

Hello World!
Hello-World?

Welcome to PU Tools!

Each row decodes into plain text while keeping blank lines and 1:1 row order intact.

Frequently Asked Questions

What is the maximum number of Base64 rows per batch?

This tool processes up to 100,000 Base64 rows at once and shows a live line count. If your list has more than 100,000 rows, divide it into smaller parts first.

How does this bulk decoder keep 1:1 row alignment with spreadsheets?

It decodes each row separately, keeps blank lines empty, and replaces internal decoded line breaks with spaces. The single Base64 Decoder joins all lines into one block instead.

What happens when a row in my list has invalid Base64?

Any corrupted or binary row receives an [Invalid Base64] label on that exact line number. Valid rows still decode normally, and the summary bar shows the exact error count.

What does Strict Mode check on each row?

Strict Mode requires valid Base64 syntax and clean UTF-8 or UTF-16 bytes on every line. Rows with spaces, invalid bytes, or unreadable control characters get marked as [Invalid Base64].

How are URL-safe strings and Data URIs handled in batch mode?

Every row converts URL-safe - and _ symbols and adds missing = padding automatically. When Auto-Detect Data URI is checked, text Data URI prefixes are stripped before decoding.

Can I batch decode accented text, Asian scripts, and emojis?

Yes. Each row decodes through UTF-8 or UTF-16 byte order marks to restore international characters and emojis.

Does batch decoding keep my lists private on my device?

Yes. All batch processing happens inside your browser memory with zero server data storage. Your Base64 lists and decoded text never leave your computer or phone.