Palindrome Checker
Check if text reads the same forwards and backwards. Find palindromic substrings and analyze character symmetry.
What is a Palindrome Checker?
A palindrome checker determines whether a piece of text reads the same forwards and backwards. Palindromes can be single words like “radar” or “level”, phrases like “A man, a plan, a canal: Panama”, or numbers like 12321.
The idea comes down to symmetry. If the first character equals the last, the second equals the second-to-last, and so on until the two pointers meet in the middle, the string is a palindrome. This tool performs that comparison after optionally normalising the input.
Normalisation is what makes phrase palindromes work. By default the checker ignores case and strips everything that is not a letter or a digit, so spaces, commas, colons, and apostrophes do not break the symmetry. You can switch to a strict comparison if you want the raw characters to match exactly.
Beyond the full-text check, the tool can analyse each word individually and can search the whole string for every palindromic substring. It also reports the normalised length so you can see exactly what text was compared, which is useful when a surprising result appears.
Because everything runs in the browser, the tool is instant and private. There is no server round trip and no data collection, so you can paste text freely.
Key Concepts
Symmetry check
Characters are compared from both ends towards the middle.
Normalisation
Case and punctuation are optionally removed before comparing.
Three check modes
Full text, per word, or all palindromic substrings.
Substring search
Finds every sequence of two or more characters that is itself a palindrome.
Live results
Analysis updates as you type or change an option.
Client-side only
Text never leaves your browser and no data is collected.
How to Use Palindrome Checker
- Enter text — Type or paste any text into the input area.
- Choose the check mode — Pick full text, per word, or find palindromic substrings.
- Set case sensitivity — Choose whether uppercase and lowercase letters must match.
- Set whitespace handling — Ignore spaces and punctuation, or include everything.
- Review the results — Read the verdict, word breakdown, or substring list — it updates as you type.
Modes and Options Reference
The checker has three modes and two option switches. The table below summarises what each one does and what you should expect on screen.
| Mode / Option | What it does | Typical output |
|---|---|---|
| Full Text | Compares the whole normalised string as one sequence. | A single verdict: palindrome or not. |
| Per Word | Splits on whitespace and checks each word separately. | A card per word, highlighting palindromes and a count. |
| Palindromic Substrings | Scans for every palindromic sequence of two or more characters. | A de-duplicated list, longest first. |
| Case Insensitive | Lowercases the text before comparing (default). | “Racecar” is accepted as a palindrome. |
| Case Sensitive | Compares characters exactly as written. | “Racecar” fails because of the capital R. |
| Ignore Spaces & Punctuation | Strips everything except letters and digits (default). | Phrases like “A man, a plan...” work. |
| Include Everything | Keeps spaces, commas, and other characters. | Strict, literal character matching. |
Worked Examples
- racecar — a classic single-word palindrome; the check succeeds immediately.
- A man, a plan, a canal: Panama — with punctuation ignored it normalises to
amanaplanacanalpanamaand passes. - hello — fails, because
hdoes not match the finalo. - 12321 — numeric palindromes are handled the same way as words.
- banana — in substring mode,
ana,anana, andnanare all reported. - Was it a car or a cat I saw — a well-known phrase palindrome that passes when spaces and case are ignored.
Tips and Common Mistakes
- Check your normalisation setting first — a phrase palindrome will fail under strict matching, which is expected, not a bug.
- Watch case traps — “Racecar” passes when case is ignored but fails when it is not.
- Numbers count as characters — digits are kept in the default normalisation, so
12321works. - Substring mode is broad — even short inputs can contain many two-character palindromes, so expect long lists.
- Empty text is not a palindrome — the tool reports nothing to check rather than a false positive.
- Compare the normalised form — the details line shows exactly what was compared, which explains surprising verdicts.
Common Use Cases
Palindrome checking is a small problem with a surprising number of uses. These are the situations where the tool earns its keep.
- Learning algorithms — see the two-pointer and expand-around-centre ideas in action.
- Puzzles and word games — verify a phrase or hunt for hidden palindromic substrings.
- Coding interviews — test edge cases such as punctuation and mixed case before writing a solution.
- Data validation — check whether identifiers or codes happen to be symmetric.
- Linguistic study — explore symmetry patterns across words and phrases.
- Teaching and tutoring — give students a visual, instant way to test their own examples.
Frequently Asked Questions
What is a palindrome?
A palindrome is a word, phrase, number, or sequence that reads the same forwards and backwards. Examples include "racecar", "madam", and "12321".
Does case matter?
You can toggle case sensitivity. By default, case is ignored so "Racecar" is still detected as a palindrome. Enable case sensitivity for strict matching.
What are palindromic substrings?
These are sequences within a longer string that are themselves palindromes. For example, in "banana", the substrings "ana" and "anana" are palindromes.
Is this tool free?
Yes, it is completely free with no limitations. All processing happens locally in your browser.
Do spaces and punctuation affect the result?
By default they are ignored, so phrase palindromes such as "A man, a plan, a canal: Panama" pass. Switch to the strict option to include everything literally.
What is the shortest palindrome?
Any single character is trivially a palindrome, and so is an empty string mathematically. This tool only reports substrings of two or more characters to avoid noise.
Can the checker handle numbers?
Yes. Digits are treated as ordinary characters, so numeric palindromes like 12321 are detected.
Does it use my text anywhere?
No. All analysis runs in your browser and your text is never uploaded, stored, or shared.