Audio caching is now done in the background rather than popping up a modal progress dialog (#112)
The audio display is automatically scrolled to the active line when audio is first opened (if that option is enabled)
Drag all selected lines when Alt is held down when dragging in the audio display (#691)
Automation now uses LuaJIT in Lua 5.2 mode rather than Lua 5.1
Text controls are "infinite" length rather than limited to 30k bytes
subs.delete can be passed a table of row numbers to delete
Add the luabins and lfs libraries to the automation environment
Filter out redundant progress updates so that they don't make everything incredibly slow
Add support for submenus in the automation menu (insert / in the macro name) (#852)
Add unicode case conversion functions to the automation module (unicode.to_upper_case, unicode.to_lower_case, unicode.to_fold_case)
Only process selected lines in the Select Overlaps macro if more than one line is selected (#1751)
Add aegisub.project_properties() to get a table with stuff that used to be in the script info section of the file (but unlike the old script info entries, it's actually always up to date) (#1747)
Fix loading automation scripts when Aegisub is installed to a path with non-ascii characters in it (#1760)
Lua functions which take a path have been patched to support UTF-8 on Windows
Add a warning when a script using a bold or italic variant of a font that doesn't actually exist, as emboldening done by the renderer may not match what is seen in Aegisub
Make the installer translatable and use the language selected in the installer for Aegisub's UI language
Fix locale issues that could lead to find/replace stripping all non-ascii characters from a file (1587)
Use localized names for languages everywhere they're displayed rather than the English names
Fix a bunch of issues with RTL locales on Windows (but unfortunately there's still some major ones remaining) (#1354)
Improve HiDPI support
Add support for IMEs in the main edit box (#1247, #1672, #1695)
Fix crash when pasting emoji into the edit box
Use the OS spellchecker service rather than Hunspell.
Make fontconfig indexing about four times as fast
Significantly speed up passing subtitles to the subtitle renderer (as much as 10x faster), making the video display less laggy with large files
Speed up indexing Matroska files
Significantly speed up reading subtitles from Matroska files
Cut idle CPU usage when Aegisub is in the background by about 90%
Cut down the disk space used a bit
Resample \be and \blur tags
Add support for converting between YCbCr matricies
Make the handling for AR-changing resampling a bit smarter
Use prettier string formatting for resampled numbers
Fix resampling drawings with AR changes
List the files which will be opened or closed in the Load/Unload files dialog
Support loading keyframes and timecodes files via drag-and-drop (#1749)
The edit box buttons (bold, italic, colors, etc.) try to do the right thing when multiple lines are selected, rather than just setting all of the lines to the active line's text
The subtitles grid has gained as Characters Per Second column, with customizable warning and error thresholds (#609)
Undo now restores the selected lines and cursor position that were active when the change being undone occured
Double-clicking on a word which is right next to a \N no longer selects the \N along with the word
Make default subtitle styles customizable: when creating a new file or importing from a format without style information, the styles from a catalog of your choice are automatically imported into the script (#962)
Add a button to open directly open the style editor for the current line's style (#1746)
Add Comment to the files which can be pasted over
Insert \N on shift-enter in the edit box
Fix incorrect cursor positions when using non-BMP unicode characters
The edit box's background color is now customizable
Fix crash when trying to open compressed tracks from Matroska
Add support for opening subtitle tracks with utterly insane CodecPrivate sections
Fix rounding error in the framerate calculations for CFR formats that sometimes lead to significantly wrong timestamps for long files
Add support for uncompressed RGB(A) files
Fix some of the issues with open-gop h264 files
Fix infinite loop when opening indexless matroska files (such as files written by x264 and not remuxed)
Fix some issues with interlaced h264
Add support for HEVC
Add option to resample the script rather than just changing the script resolution when opening a video with different resolution (1382)
Several of the tools have been somewhat restyled to make them less obstructive
Hide drag handles for commented lines
Don't automatically select all control handle in the vector clip tool when switching to it, as there's now box selection of handles
Update all selected lines when the origin is dragged in the rotate tools