Word Ladder
Turn one word into another a letter at a time, with daily and random ladders at three levels and a solver for any pair.
A word ladder turns one word into another by changing one letter at a time, and every step must be a real word: COLD, CORD, CARD, WARD, WARM. Play a new ladder every day, or random ones of 3 to 6 letters at three levels, and try to match par, the fewest steps it takes.
The Solver finds every shortest ladder between any two words of 2 to 15 letters. It all runs in your browser, and your ladders and stats stay on this device.
How to use it
Type the next word and press Enter. It must have the same length, differ from the word above in exactly one letter, and be in the site's word list, which includes rarer words that word games accept. A word already on the ladder is refused, so a ladder never loops. The changed letter of each step is highlighted. Tap an earlier word to go back to it, or use Undo for one step.
Steps are letter changes, so COLD to WARM through CORD, CARD and WARD is 4 steps. The result is shown against par: “par”, “−1” for a step under, “+2” for two over. Hint adds the next word of a shortest ladder from where you are, or takes you back to that word when it is already on your ladder, and Give up shows one from the start; either way the ladder counts as played, not solved, in your stats.
- Daily: one ladder a day, the same for everyone, from the date where you are. Par rises through the week: Monday 3, Tuesday 4, Wednesday 4, Thursday 5, Friday 6, Saturday 6, Sunday 7. A daily you are playing at midnight stays on the page until you finish it. Opened on a later day, the page shows that day's ladder instead, and an earlier one you had started counts as played, not solved.
- Random: a ladder of 3, 4, 5, 6 letters, at Easy (par 3–4), Medium (par 5–6), Hard (par 7–9).
In the Solver, type two words of the same length. It lists up to 50 shortest ladders and counts the rest. With Common words only on (the default), every step is a common word; off, any word in the list can be a step. A search stops after 2 seconds. When both words are in the list, Play this ladder turns the pair into a game, and its share link challenges someone else to the same two words.
How par and the solver work
Each word is joined to every word one letter away. To find those quickly, each word is filed under its patterns with one letter blanked out: COLD under _OLD, C_LD, CO_D and COL_, so the words sharing a pattern are its neighbours. A breadth-first search then spreads out from the start one step at a time, which reaches the target first along a shortest ladder, and remembers every way into each word to count all the shortest ladders at once.
Par is the fewest steps through common words: those in SCOWL's medium-sized list (size 50 or below), the source of the site's word list. Puzzles start and end on familiar words, and always have a ladder at par through common words, so no obscure word is ever needed. A rarer word can open a shortcut, so you can finish under par. A pair played from the Solver or a link that only rarer words join takes its par from every word in the list.
A ladder needs at least as many steps as the letters that differ between the two words, since each step changes one letter. COLD and WARM differ in all four, so 4 steps is the least possible, and a ladder of 4 changes each letter exactly once. Most pairs need more: a letter is changed and later changed again, to reach a word the next step needs.
Worked example
COLD to WARM through common words
- Shortest ladder
- 4 steps
- Shortest ladders
- 4
- First, alphabetically
- COLD → CORD → CARD → WARD → WARM
Every shortest ladder changes each of the four letters once, in an order that keeps every step a word.
Frequently asked questions
See also
- Word Unscrambler — to find every word in a set of letters.
- Hangman — for another word game, one letter at a time.