Lipogram & Isogram Checker

Constrained writing sets rules on the letters you may use, and finding a slip by eye is surprisingly hard. A lipogram avoids one or more letters entirely; an isogram is a word in which no letter repeats. This tool checks both and highlights every word that breaks the rule, so you can fix it.

Checking a lipogram

Type the letters to avoid — e is the classic choice, because it is the most common letter in English — and paste or write your text. Every word that contains a forbidden letter is highlighted in the text, and hovering over a highlight shows which letter it contains. The notice above tells you how many words need changing; when it says none, the text is a valid lipogram. Accented forms count as their letter, so é and è are caught when e is forbidden.

Why it is harder than it sounds

Avoiding e rules out the, he, she, be, are and almost every past tense ending in -ed. Writers must rephrase constantly, which is exactly the point: the constraint forces new word choices and fresh sentences. Short exercises without a, i or o are good warm-ups, and avoiding several letters at once quickly becomes a serious puzzle.

Famous lipograms

Ernest Vincent Wright published Gadsby in 1939, a novel of about 50,000 words without the letter e. Georges Perec, a member of the French Oulipo group devoted to constrained writing, wrote La Disparition (1969) without e; Gilbert Adair’s English translation, A Void, keeps the rule. Perec later wrote Les Revenentes, which uses no vowel other than e.

Isograms

Switch to the isogram check to find words in your text that repeat a letter, highlighted in place. The counters show how many words there are, how many are isograms and whether the entire text is one, which only very short texts manage. The longest isograms in your text are listed with their letter counts. Isograms are popular in word games and are useful for ciphers: a keyword with no repeated letters, such as “lumberjack”, fills a cipher alphabet without gaps.

Ideas for the classroom

Ask students to describe their weekend without the letter a, to write a six-word story without e, or to find the longest isogram in a reading passage. The checker makes marking instant, and highlighting shows students exactly where to rework a sentence.

Private

The text you check stays in your browser.

A worked example

With e forbidden, the sentence “A big dog runs fast across a dusty road” passes: none of its words contains e. Change “road” to “street” and the checker highlights street, with a tooltip naming e. In isogram mode, the same sentence shows across highlighted, because s appears twice, while dog, runs, fast, dusty and road are isograms; the longest isograms listed would be dusty, runs, fast and road.

Working through the highlights

Fix highlighted words one at a time and the highlights update as you type. Synonyms are the usual fix — “road” for “street”, “big” for “large” — but sometimes a whole sentence needs restructuring, which is where lipograms become a creative exercise rather than a search-and-replace job.

Related tools

Use every letter instead with the Pangram Checker, compare letter sets with the Anagram Checker, build poems from first letters with the Acrostic Helper, or replace words in bulk with Find and Replace.