In practice I find both spellings being used. From a logical point of view, "allright" (as in: "all's right — everything is fine") seems correct. However, I recall hearing that "alright" is the preferable variant.
Is there consensus over which to use? Do they possibly even mean something different?
Best Answer
Wiktionary marks alright as an "alternative spelling" of all right, and allright as a "common misspelling" thereof. Merriam-Webster only has entries for alright and all right, and this usage discussion:
The stats from the Corpus of Contemporary American English and the British National Corpus look as follows:
This suggests that alright is much more popular in Britain than in the US. However, the Corpus of Historical American English paints the following picture:
X axis: year, Y axis: incidences per million words.
So, alright seems to be gaining popularity in the States as well.
Lastly, the fact that all right loses one L when written as one word is not peculiar in the least — just think of already, almost, although, albeit, almighty, altogether, and any number of other words formed this way.