What is a word ladder solver?
A word ladder solver finds the shortest chain of words that turns one word into another, changing a single letter at each step. Enter a start word and an end word of the same length, and Unknot Words searches the whole US (NWL) or UK (CSW) word list to show the shortest possible ladder, plus other ladders of the same length so you can choose the one with the most familiar words.
By Unknot Words · Last updated
How to use the solver
- Enter a start word and an end word. They must have the same number of letters, from 2 to 8. Use the swap button to try the ladder in the other direction.
- Choose a dictionary. The UK list is larger, so it can sometimes find a shorter ladder or connect words the US list can't.
- Find the ladder. The first shortest ladder appears as numbered rungs, with the changed letter highlighted at each step. Up to nine more ladders of the same length are listed below it.
Worked examples
LEAD to GOLD is the alchemist's dream, and it takes just three steps: LEAD, LOAD, GOAD, GOLD. It is the only three-step ladder in the US dictionary.
COLD to WARM takes four steps, and the US dictionary has six different four-step ladders. The classic is COLD, CORD, CARD, WARD, WARM. Others pass through WORD and WORM instead. The UK dictionary adds a seventh.
Some pairs need far more steps. WHEAT to BREAD needs six: WHEAT, CHEAT, CLEAT, BLEAT, BLEAK, BREAK, BREAD, and that is the only ladder of that length in the US list.
A puzzle with a long history
Lewis Carroll, the author of Alice's Adventures in Wonderland, introduced the puzzle in 1879 under the name “Doublets”. He challenged readers of Vanity Fair to turn HEAD into TAIL and to make similar transformations in as few steps as possible. Since then the puzzle has appeared as word golf, laddergrams and word links, in newspapers, classrooms and, more recently, daily puzzle apps.
How the solver finds the shortest ladder
Think of every word as a point on a map, with a path between any two words that differ by one letter. The solver uses a breadth-first search: it visits every word one step from the start, then every word two steps away, and so on, until it reaches the end word. Because it explores in rings of increasing distance, the first ladders it finds are guaranteed to be the shortest. It then lists the equally short ones in alphabetical order.
Some words are islands. Long words in particular often have no neighbors at all, because changing any single letter produces a non-word. When that happens the solver tells you no ladder exists in that dictionary.
Tips for solving word ladders yourself
- Fix the letters that already match. In COLD to WARM, no letter is in the right place, but in LEAD to GOLD the D already is, so you only need to change three letters.
- Change vowels early. Swapping a vowel (LEAD to LOAD) often opens up many more neighbors than changing a consonant.
- Work backwards. If you are stuck, list the words one step away from the end word and aim for one of those instead.
- Use common endings. Words ending in -ARD, -ORD, -ATE and -ING tend to have many neighbors, which makes them good stepping stones.
Word ladders build spelling and vocabulary because every step forces you to test whether a letter pattern is a real word. For classroom ideas, see word games in the classroom. To check whether a single word is allowed in Scrabble, use the word checker.
Frequently asked questions
What are the rules of a word ladder?
Start with one word and reach a target word of the same length by changing exactly one letter at a time. Every word in between must be a real word, and letters cannot be added, removed or rearranged.
Who invented word ladders?
Lewis Carroll, the author of Alice in Wonderland, published the puzzle as "Doublets" in Vanity Fair in 1879. His examples included turning HEAD into TAIL. The puzzle is also known as word golf, laddergrams and word links.
Why does the solver show several ladders?
Many pairs of words can be joined by more than one ladder of the same, shortest length. The solver lists up to ten of them in alphabetical order, so you can pick the one with the most familiar words.
Why can't the solver connect my two words?
Some words have no neighbors at all, and long words are often isolated because few words differ from them by a single letter. If no ladder exists in one dictionary, try the other; the UK list contains more words and connects more pairs.
How long can the words be?
Both words must have the same length, from 2 to 8 letters. Ladders between three-, four- and five-letter words are the most common, because short words have the most neighbors.
Is the ladder guaranteed to be the shortest?
Yes. The solver uses a breadth-first search, which explores every word one step away, then two steps away, and so on, so the first ladders it finds are always the shortest possible in the selected dictionary.