Base64 Multi-line Merge

Multiline Base64 Input
0 lines · 0 chars

Online Base64 merge tool that joins multi-line Base64 strings into a single line, removing all line breaks, spaces, and tabs. Runs locally in your browser with nothing uploaded, merging instantly as you type.

Related

Base64 Split

Base64 Cleaner

Base64 Formatter

Base64 Padding Tool

Base64 Encode

Base64 Decode

What is Base64 multi-line merge?

Base64 multi-line merge is the operation of joining multi-line Base64 strings—broken by line breaks or whitespace—back into one continuous single-line string. Many systems (email MIME, logs, JSON fields) automatically wrap Base64 output at 76 characters or insert whitespace during transport, so the receiver must merge them first to restore the original payload.

**The essence of merging:** it only removes whitespace characters (spaces, line breaks \n, carriage returns \r, tabs \t) from the input string. It does not decode Base64 or alter any characters.

**Difference from Base64 decoding:** decoding turns Base64 back into the original binary or text; merging only rearranges the physical layout of the same string into a single line, leaving the content unchanged.

**Typical uses:** ① Restoring Base64 content wrapped by email MIME; ② Collapsing Base64 fields with line breaks inside JSON into a single line for easy copy; ③ Reassembling multi-line Base64 from logs or terminals before further processing; ④ Tidying the Base64 credentials in the HTTP Authorization header.

Use Cases

  • Restore Base64 content wrapped by email MIME into a single line for further decoding or transport
  • Tidy Base64 fields with embedded line breaks inside JSON strings into a single line for easy copy and paste
  • Reassemble Base64 printed across multiple lines in logs or terminals before secondary processing
  • Format the Base64 credentials in an HTTP Authorization header into a clean single-line string
  • Clean Base64 copied from web pages or documents that contains stray whitespace into one continuous string

How to Use

  1. Paste or type a multi-line Base64 string in the left input area (line breaks, spaces, and tabs are allowed).
  2. The tool automatically merges it into a single line shown in the right output area; check the line and character counts in the status bar.
  3. Look at the "✓ valid" or "✗ invalid format" hint under the output area to confirm the merged string is valid Base64.
  4. Click "Copy" to copy the merged result, or click "Download" to save it as a txt file.

Features

  • Instant merge: input is automatically merged into a single line after a 300ms idle period
  • Remove all whitespace: strips spaces, line breaks, carriage returns, and tabs
  • Format validation: the output area shows "✓ valid / ✗ invalid format" status
  • One-click copy: the merged result can be copied straight to the clipboard
  • Download as txt: save the result as a merged-base64.txt file
  • Line and character counters: shown live in the status bar at the bottom
  • PC / mobile responsive: resizable split panes on desktop, tab switching on mobile
  • Pure browser processing: content is never uploaded to any server

Best Practices

Keep the original multi-line input

preserve the original as a reference before merging, in case you need to roll back.

Validate after merging

use the output area's validity hint or the "Base64 Validator" tool to confirm the merged string is valid Base64.

Split very large inputs

for huge strings, split into chunks and merge separately to avoid browser lag.

Handle URL-safe separately

for URL-safe Base64 (using - and _), use the dedicated tool to avoid confusion with standard Base64.

Split DataURL first

when merging a DataURL, first use the "Base64 DataURL" tool to separate the prefix and the payload, then merge each part.

FAQ

How is merge different from "clean / format"?

"Merge" only removes whitespace and joins into one line; "clean" additionally removes illegal characters and fixes padding; "format" does the opposite, splitting a single line into fixed-width chunks. This tool only merges and does not modify any Base64 character.

Will the character count match after merging?

Yes. Merging only deletes whitespace, so the Base64 characters themselves are unchanged. The merged length equals the original length with all whitespace removed.

Decoding fails after merging—what should I do?

Non-Base64 characters may have crept in (such as stray CJK or special symbols). First use the "Base64 Validator" tool to check the character set, then the "Base64 Cleaner" tool to strip impurities.

Does it merge URL-safe Base64?

Yes. URL-safe Base64 uses - and _ in place of + and /, and this tool removes whitespace from it as well. To further distinguish the two variants, use the dedicated "Base64 URL Safe" tool.

Does merging alter the Base64 content?

No. This tool only removes whitespace and never changes any Base64 character such as A-Z, a-z, 0-9, +, /, or =, so the decoded result before and after merging is identical.

Can it merge a Data URL with a data: prefix?

It can merge it. This tool does not strip the data:image/png;base64, prefix; it only removes whitespace between the prefix and the payload. To separate prefix and payload, use the "Base64 DataURL" tool.

Can it merge hundreds of lines of Base64 at once?

Yes. There is no hard limit on input length as long as the browser has enough memory. For best responsiveness, keep a single input under about 100 MB.

Is the content uploaded to a server?

No. This tool runs entirely in the browser. All merging happens locally and your input never leaves your device.

Can the merged result be decoded directly?

Yes—copy the merged single-line Base64 into the "Base64 Decoder" tool to restore the original content.

Glossary

Base64
An encoding that represents binary data using 64 printable characters. This tool only handles the physical layout of a Base64 string and does not encode or decode it.
MIME line wrapping
In the email standard, Base64 output is automatically wrapped at 76 characters for easier transport. This tool can merge such wrapped Base64 back together.
Whitespace characters
Invisible characters such as spaces, tabs (\t), line breaks (\n), and carriage returns (\r). The merge operation of this tool removes exactly these characters.
Merge
Only concatenates the string and removes whitespace; it does not modify any Base64 character. It differs from more complex operations such as decoding, encoding, or cleaning.

Authoritative References