To help you with quality assurance of your subtitle scripts, Aegisub features a complete spell checker. It uses the Hunspell library, which is based on OpenOffice.org's MySpell, which means it's at least as good as one you'd find in a sophisticated word processing program. It can be found in the Subtitles menu -> Spell Checker. It also spell-checks as you type and can to some degree be controlled from the subtitle edit box's right-click menu (see editing subtitles).
The spell checker dialog will go through all misspelled words it can find in your script. The area in the lower left of the box displays suggestions to replace the misspelled word with; to the right there are a number of buttons:
At the bottom of the dialog box there is a dropdown box to choose the spell checker language.
The Windows version of Aegisub comes with a US English dictionary. Installers for many other languages are available on our website. If we don't supply a dictionary for your language, check Mozilla's set of dictionaries, or simply Google for "hunspell <language> dictionary". We welcome submissions of additional dictionaries to package - it can sometimes be hard for us to find dictionaries for languages which none of the developers speak.
The OS X version of Aegisub includes all of the dictionaries we have.
On Linux your distribution's package manager should have hunspell
dictionaries. You may need to set the dictionary
path to the location where they are installed; one
common location is