Palindrome Checker

Check words, phrases, numbers, and batches after ignoring spaces, punctuation, and case.

Last reviewed: June 2026
Reviewed by , software engineer - last updated June 2026

New to this tool? Click here for instructions

Enter a word or phrase above to check if it is a palindrome.

How to Use the Palindrome Checker

Use the Check tab for one word, phrase, number, or mixed string. Type or paste the text and the result updates in the browser. The tool shows the cleaned string, the reversed string, and a character map for shorter matches so you can see exactly why the input passed or failed.

Use Batch mode when you have a list of candidate palindromes. Paste one item per line and the table marks each row as yes or no after applying the same cleanup rule. Use Famous Palindromes when you want quick sample strings for demos, classroom exercises, interview prompts, or test cases.

How It Works

The checker runs local JavaScript only. It converts the input to lowercase, removes characters outside ASCII letters and digits with a regular expression, reverses the cleaned string, and compares both values. That means A man, a plan, a canal: Panama! is evaluated as amanaplanacanalpanama.

This approach is intentionally transparent. You can inspect the exact cleaned and reversed values before trusting the result. The comparison is fast for normal writing samples because the browser only needs to scan the string and reverse the remaining characters.

Tips, Edge Cases, and Limitations

The cleanup rule is ASCII-focused: a-z and 0-9 are kept, while punctuation, whitespace, symbols, accented letters, emoji, and other scripts are ignored. That is useful for common English phrase puzzles, but it is not a full Unicode grapheme-cluster palindrome engine.

For data-cleaning work, check the cleaned value before copying a result into a report. If accents, non-Latin scripts, or emoji matter, normalize the text in a dedicated Unicode workflow first and treat this checker as a lightweight local triage tool.

Sources Checked

The implementation follows standard JavaScript string operations documented by MDN: String replace for cleanup and Array reverse for reversing the split characters.

Frequently Asked Questions

A palindrome is a word, phrase, number, or sequence that reads the same forwards and backwards when you ignore spacing, punctuation, and capitalization.
The tool removes non-alphanumeric characters, converts the text to lowercase, and compares the cleaned string to its reverse using the two-pointer technique.
Yes, the tool can check numbers and mixed content. It will ignore non-alphanumeric characters and focus on the alphanumeric characters to determine if the input is a palindrome.
Batch mode allows you to paste a list of words or phrases (one per line) and check them all at once. The results will appear in a table with pass/fail indicators.
The Famous Palindromes tab includes well-known words, phrases, and numeric examples so you can compare how punctuation, spacing, and case are handled.

Example walk-through

Phrase check: Panama palindrome

Step 1. Enter A man a plan a canal Panama in Check mode.

Step 2. The cleaned value becomes amanaplanacanalpanama; spaces and capitalization are ignored.

Step 3. The reversed value is also amanaplanacanalpanama, so the result is marked as a palindrome.

Input: A man a plan a canal Panama
Cleaned: amanaplanacanalpanama
Reversed: amanaplanacanalpanama
Result: Palindrome