OptiFine¶

You download OptiFine once, from optifine.net. Xol checks the file and keeps its own copy. From then on, every start of that Minecraft version uses it while the OptiFine add-on is on. Xol never bundles, mirrors or uploads OptiFine.

Why Xol cannot include it¶

OptiFine's license does not allow redistribution, and its download page is paid for by advertising. A launcher that bundled OptiFine, mirrored it or fetched it behind the page's back would break those terms. So the download is yours, once, from optifine.net's own page. The launcher says: "OptiFine's licence doesn't let launchers include it, so it comes from its own page, once."

The list of known builds holds names, sizes and checksums only. There is no download address in it.

The OptiFine add-on¶

Since 0.3.0 OptiFine is an add-on, not a profile of its own. The main screen shows an OptiFine switch next to the Minecraft version, and the same switch is in Settings ▸ Instance ▸ OptiFine as "Use OptiFine with Minecraft 1.8.9". The setting is per Minecraft version and is saved the moment it changes.

The line under the switch says what it will do, in plain words: "Off", "Not added yet", or the build, for example "M5". Switch it off and Xol takes its copy out of the instance at the next start. The copy Xol keeps is untouched, so switching it on again needs no download.

Switching OptiFine on before a file has been added opens the Add OptiFine dialog.

Add it, step by step¶

1. Open the dialog. Any of these opens Add OptiFine: the quiet line Add OptiFine for better performance on the main screen, Settings ▸ Instance ▸ OptiFine ▸ Add OptiFine…, or switching the OptiFine add-on on. That line is the launcher's wording; Xol has measured nothing. Its close button hides the suggestion for good.
2. Press Download on the OptiFine page. When the dialog opens, Xol opens optifine.net's own page for the recommended build in a window of its own: OptiFine_1.8.9_HD_U_M5.jar for 1.8.9, OptiFine_1.7.10_HD_U_E7.jar for 1.7.10. Press Download on that page. The dialog reads "Press Download on the OptiFine page. Xol adds OptiFine HD U M5 the moment it finishes." Other builds on optifine.net opens the full list in your browser instead.
3. Done. "OptiFine HD U M5 added." Below that the dialog says which profiles now start with it and how far the file could be checked.

The first time you press Play on a Minecraft version whose OptiFine add-on is on and has no file yet, Xol opens this dialog by itself, once ever for that version. Press Download and the game starts with OptiFine, or press Start without OptiFine. Either way the game starts when the dialog closes.

Other ways in. While the dialog is open, Xol also looks in your Downloads folder, so a file you downloaded in your own browser is added the moment the download finishes. If your browser saves somewhere else, press Choose the file… and pick the jar.

The OptiFine page window¶

The window shows optifine.net's real page, its advertising included. It only shows pages on optifine.net and refuses to open anything else. It keeps no cookies or cache after it closes, grants the page no permissions, and accepts only a download named like an OptiFine build for that Minecraft version. The downloaded file goes straight to Xol, is checked like any other file, and the window closes.

What Xol looks at in your Downloads folder¶

• Only while the Add OptiFine dialog is open. Looking starts when the dialog opens and stops when it closes. Closing the launcher window stops it too, and it gives up by itself after 30 minutes.
• It reads the list of file names in your system's Downloads folder, and never goes into folders below it.
• It looks further only at names that match OptiFine_<Minecraft version>_HD_U_….jar (or preview_OptiFine_…) for the selected Minecraft version. No other file is opened, read, measured or checksummed.
• A match must be an ordinary file directly in that folder. A link or a folder with such a name is ignored.
• An unfinished download is left alone: a partial file beside it (.crdownload, .part, .download, .partial, .tmp, .opdownload), an empty file, or a size that is still changing. A file counts as finished once it has not changed for a second and a half.
• A finished file goes through the checks below. A refused file is reported once in the dialog, and Xol keeps looking. If several files match, the newest is tried first.
• Xol never writes, moves, renames or deletes anything in Downloads, and nothing about that folder is sent anywhere. Your download is copied; you can delete it afterwards.

How the file is checked¶

Before anything is copied, the file is inspected as data. Nothing in it is run.

Known builds¶

Xol carries a short list of OptiFine builds. A SHA-256 is listed only where more than one independent public source agrees on it.

Update OptiFine¶

Open Settings ▸ Instance ▸ OptiFine ▸ Update or remove…. The dialog is titled Update OptiFine and works the same way: a newer build you download replaces the one Xol keeps.

• When Xol suggests a newer build than the one you have, the main screen says so once, with Update to and the build name. Its close button means that build is not suggested again.
• While updating, files that were already in Downloads do not count, so an old download lying there never replaces a newer build. Only a download that arrives while the dialog is open is taken.
• Choose the file… asks first when you pick an older build than the one Xol keeps: "Nothing was changed", with Keep the current build or Use the older one anyway.
• The new copy reaches the instance the next time the game starts.

Switch it off¶

Switch the OptiFine add-on off on the main screen, or in Settings ▸ Instance ▸ OptiFine. Xol takes its copy out of the instance the next time the game starts. The copy Xol keeps stays, so switching it on again needs no download. The choice is stored per Minecraft version in launcher.json.

If the build you added cannot start with Forge, the switch cannot be turned on and says "this build cannot start here".

Remove it¶

Remove OptiFine is in the same dialog. One press removes the copy Xol keeps for that Minecraft version and every copy Xol placed in an instance of that version: "OptiFine removed. Minecraft 1.8.9 starts without it. Adding it again takes the same one download."

Your original download is never touched, and neither is an OptiFine jar of your own. While a game is starting or running, nothing adds, replaces or removes OptiFine: "Close the game before adding or changing OptiFine. Your download stays where it is."

Your own OptiFine jar¶

Xol only ever replaces or removes files it placed itself. If you keep optifine.net's own file (OptiFine_….jar) in your my-mods folder with the Forge mods add-on on, Xol adds no second copy, because the game does not start with two. A file at mods/OptiFine.jar that Xol has no record of is treated as yours and left alone.

Where Xol keeps it¶

An OptiFine file that an older launcher placed in an instance becomes the copy Xol keeps for that Minecraft version.

Every rejection message¶

A refused file is reported in the dialog, as " was not added." followed by one of these. Xol keeps looking.

Brand and servers¶

With or without OptiFine, Xol reports the client brand Xol. See Multiplayer and fair play.