Palindrome Checker

A palindrome reads the same forwards and backwards: level, racecar, or the sentence "A man, a plan, a canal: Panama". The checker ignores spaces, punctuation and capital letters by default, which is how people normally judge phrases, and shows the cleaned text forwards and backwards so you can see where a near miss goes wrong.

How to use it

1. Type or paste a word, phrase or number.
2. Choose whether to check everything as one phrase or each line on its own.
3. Keep the ignore option on for sentences, or switch it off for a strict character-by-character comparison.
4. Read the verdict and the side-by-side comparison.

When it helps

• Settling an argument about whether a phrase counts.
• Testing a list of candidate words in one go using line mode.
• Checking numbers like 12321.
• Proofing a palindrome you wrote for a puzzle or a poem.

Good to know

• In strict mode almost every real sentence fails, because spaces and commas won't mirror. That's expected.
• When a phrase fails, the forwards and backwards lines make the first mismatch easy to spot.
• Letters from other alphabets are compared as they are, so it works beyond English.

What counts as a palindrome

The strict definition is a sequence that reads the same in both directions, character for character. Words like level, radar and civic qualify. Phrases usually need looser rules, where spaces, punctuation and capital letters are ignored, because otherwise "A man, a plan, a canal: Panama" would fail on its commas. This tool defaults to the looser rule and lets you switch it off.

Numbers can be palindromes too: 121, 12321 and 1001 all read the same reversed. Some dates are famous for it, such as 02/02/2020 when written without the separators.

Worked example: spotting the first difference

Take the phrase "Never odd or even". With loose rules it becomes neveroddoreven, and reversed it's nevero ddoreven, which reads "neveroddoreven" both ways, so it passes. Now try "Not a palindrome": the cleaned text is notapalindrome and the reversed text is emordnilapaton, and the first characters, n and e, already differ.

That side-by-side view is the most useful part. When a long phrase fails, scan from the ends towards the middle and the first mismatch usually shows which word is breaking the pattern.

Uses beyond word games

Teachers use palindromes to introduce string reversal in programming, and the check is a classic interview question. If you are writing one yourself for a puzzle, paste candidates in line mode to test many at once, then keep the ones with a tick.

Remember that loose rules ignore case and spacing but not letters, so a typo changes the result. If you expect a pass and get a fail, compare the two lines, find the odd letter out, and fix it.

Questions