Letter Swap

hrap is a word you know with two of its letters in each other's places. Put them back and it is harp. That is the whole game: four letters, six possible exchanges, and exactly one of them spells a real word. Each round adds another word, and the deal is ordered so the letters get wordier as you go — the last round's four letters usually spell at least one other real word as well, which is exactly what makes them hard to read. One shared allowance of wrong exchanges covers the whole run, so guessing your way through is not affordable.

It runs entirely on your device: 0 network requests, works offline. No ads, no account, nothing to buy, and no betting, money or prizes of any kind.

1. Read the four letters on the board. They are a real four-letter word with exactly two of its letters exchanged, and the string in front of you is never a word itself.
2. Focus the board — click it, or press Tab until it is outlined.
3. Move the cursor with ← and →. ↑ and ↓ jump two places, which is the exchange across the middle of the word — the one the eye skips.
4. Lift a letter with Enter or Space. It is marked ▲ lifted, and lifting costs nothing.
5. Press a second letter to exchange the two. Press the same letter again, or Esc, to put it back — also free.
6. Right? The word is added to your list with a ✓ and the next round's letters appear. Wrong? A ✕, the letters stay where you put them, and one wrong exchange comes off your allowance.
7. Two identical letters cost nothing to exchange, because nothing moves.
8. Put all five words right before the wrong exchanges run out.

How do you spot which two letters have been swapped in a word?

Read it one letter at a time, out loud if you can, instead of looking at its shape. Whole-word reading is what makes a transposition invisible — the outline of hrap is close enough to harp that the fast, shape-matching part of reading hands you "harp" and moves on, which is exactly why proofreaders miss transposed letters in their own writing. Three habits beat it. First, check the first and last letters, because they anchor the shape and an exchange that moves one of them is the easiest to catch. Second, look for a consonant run that English does not start with: hr, tl, sm at the front of a word is a strong signal that the first letter has moved. Third, find the vowel. A four-letter word almost always has one in position two or three, so a vowel sitting at the end — litf, sulg — tells you where the exchange happened before you have recognised the word at all.

Is there always exactly one answer?

Yes, and it is checked before the letters are ever shown to you. Every word in this site's list is run through all six of its possible exchanges, and a candidate is kept only when two things hold: the resulting string is not itself a word, and exactly one of the six exchanges turns it back into a word. The check is exhaustive, not sampled — six lookups, all of them made. So the round you are given always has an answer, never has two, and no "Play again" can produce a board that cannot be finished.

Why is one word missing from the game?

spot is the only word in the list of 1292 that can never be dealt, and the reason is a nice one: its letters spell five words. Exchange its second and fourth letters and you get stop, which is already a word, so there is nothing to repair. Every other exchange leaves a string that two or three different exchanges would repair — opst goes to post, spot or opts — so there would be no single right answer. The wordiest four letters in the list are the ones that cannot make a fair puzzle.

How many wrong exchanges do I get?

Four, five, six or seven, and which one you get is measured rather than chosen. Every dealt letter set is counted against the whole word list to see how many other real words it spells, and those counts are added up across the five rounds. A wordier deal forgives more, because the mistakes it causes are the puzzle working rather than you failing. It is deliberately tight either way: guessing a single word blindly costs up to five wrong exchanges, and no run ever grants that many for five words, so reading beats guessing every time.

Is there any money or in-app purchase in this?

None, and there never will be. No currency, no prizes, nothing to buy, no lives to refill, and nothing here you could ever put money on. It is a word puzzle, and that is all of it.

Can I play it with a keyboard or a screen reader?

Both, with the same rules. Arrows move, Enter or Space lifts and exchanges, Esc puts a lifted letter back. Every letter is a real button whose spoken label gives its position and whether it is lifted, and the live region reads out the round, the letters one by one, the tries left and the verdict after every move. Lifted letters carry a ▲, restored words a ✓ and a wrong exchange a ✕, so nothing at all depends on telling colours apart.

Does it work offline?

Yes. Once the page has loaded once, the whole game is on your device — the word list, the puzzle pool, the checking and the scoring. Nothing is fetched while you play, and there is no server involved at any point.

Words are four letters, drawn from this site's own list of 1292 common English four-letter words, and 1291 of them can be dealt. A run is five rounds, ordered so the letters get wordier as you go. The allowance of wrong exchanges runs from four to seven and is derived from how many other words the dealt letters spell. There is no timer, no streak to protect and no hint button: the count of tries left is the only pressure, and the letters in front of you are all the information the answer needs.

Anagram Rush gives you the letters loose and asks for the word, with no clue about how far they have moved. Prefix Hunt fixes the first three letters and asks which last letters finish a real word. Word Hunt hides whole words in a grid and asks you to read a line before claiming it.

Bookmark this page (Ctrl+D, or ⌘D on Mac) or install the app — it works offline the next time you need it.