Does it add the suffix to every line, or just once?

The suffix is added once, to the very end of the whole input, not to each line.

Is a separator inserted before the suffix?

No. The two are joined exactly as given, so include any space, dot, or punctuation you need as part of the suffix itself.

What happens to a trailing newline in my text?

It is preserved, so the suffix lands after it and ends up on a line of its own. Trim the text first when the suffix should sit on the same line as the content.

String Suffix Adder Online - Append Text to a String

Overview

Introduction

Appending a fixed suffix to text, a file extension, a unit, closing punctuation, is a one-line operation in code but convenient to have as a standalone tool.

It runs entirely client-side, so nothing you paste is ever uploaded to a server.

What Is String Suffix Adder?

A suffixing tool that concatenates your chosen suffix onto the end of the input text.

It runs entirely client-side as part of this site's String Tools collection, so nothing you paste is ever uploaded to a server.

How String Suffix Adder Works

The tool simply returns `input + suffix`.

The transformation happens synchronously in JavaScript the moment you type, with no network round trip involved.

When To Use String Suffix Adder

Use it to quickly append a file extension, a unit of measure, or trailing punctuation to a value.

It's a fast way to get the answer without opening a code editor, a REPL, or writing a one-off script just to check.

Often used alongside String Prefix Adder and Find & Replace Tool.

Features

Advantages

Simple and predictable, a direct string concatenation.
Concatenates without trimming, so any trailing whitespace in your text survives exactly as it was.
Treats the input as one value, which keeps multi-line text intact rather than altering each line separately.

Limitations

Adds the suffix once to the whole input, not per line.
Appends once at the very end, so adding a suffix to each item of a list means running it once per item.

Examples

Appending a greeting

Input

Hello

Output

Hello, world!

With suffix ', world!', the result is the input followed directly by the suffix.

Best Practices & Notes

Best Practices

For per-line suffixing across multiple lines, process each line individually.
Include the separator in the suffix, such as a leading dot for a file extension or a space before a unit.
Check for a doubled separator when the text already ends with one, since nothing is deduplicated for you.

Developer Notes

The implementation is a single string concatenation (`input + suffix`), with no per-line splitting.

String Suffix Adder Use Cases

Appending a file extension to a filename
Adding a unit of measure to a numeric value
Appending closing punctuation to a sentence

Common Mistakes

Expecting the suffix to be added to every line of multi-line input.
Adding a file extension to a value that already carries one, which produces a doubled extension rather than replacing it.

Tips

Use Add a Prefix to a String for the equivalent operation at the front of the text.
Pair it with the String Prefix Adder to wrap a value on both sides in two quick passes.

String Suffix Adder