Updating Unity is one of those tasks that feels routine until something goes wrong. Most updates go smoothly, but every developer has a story about a project that broke after an upgrade: a plugin stopped working, a build behaved differently, or a game that ran fine yesterday suddenly refused to launch. One small habit makes recovery far easier, and it costs almost nothing: backing up the runtime files before you update. monobleedingedge is the folder at the centre of that habit, because it holds the Mono runtime your game depends on.
Why a Backup Matters Before an Update
A Unity update can change the runtime your project uses. New versions ship with newer runtime libraries, updated configuration, and sometimes different default behaviour for garbage collection or scripting. In most cases those changes are improvements, but if your project depends on a specific behaviour, or if a third-party plugin was built against the older runtime, the update can introduce subtle problems that are hard to trace.
Having a backup gives you a way back. If the updated project misbehaves, you can compare the old and new runtime folders, restore the previous setup, and confirm whether the runtime change is really the cause. Without a backup, you are left guessing, and guessing during a broken build is stressful. The backup does not need to be fancy; it just needs to exist before you press update.
What to Back Up, Exactly
There are two copies of the runtime worth knowing about. The first lives inside your Unity editor installation, in the editor’s data directory, and it powers the editor itself and play mode. The second lives inside each built game, next to the game’s data folder, and it powers the shipped game. For project safety, the editor copy matters most, because that is what your development workflow depends on.
A practical backup is a plain copy of the whole folder, stored somewhere outside the Unity installation, with the Unity version in the folder name. For example, a folder named “MonoBleedingEdge-2022-3-backup” tells you at a glance which version it belongs to. Copying the folder is enough; you do not need special backup software, and you do not need to compress it unless disk space is tight.
Step-by-Step: A Safe Backup Routine
Start by closing the Unity editor and any running builds. Copying runtime files while the editor is running can produce an inconsistent copy, because files may be locked or in use. Once everything is closed, locate the MonoBleedingEdge folder inside your editor installation and copy it to your backup location. If you work on several Unity versions side by side, repeat the step for each version you actively use.
Next, note down the version numbers. A short text file next to the backup, recording the Unity version, the date, and the project you were working on, turns a pile of folders into a useful archive. Months later, when you wonder which backup belongs to which project, that note saves real time. Finally, verify the backup copied completely by comparing folder sizes or file counts. A backup you have never checked is only a hope, not a safety net.
Restoring After a Problem
If an update causes trouble, resist the urge to change many things at once. First, confirm the problem is runtime-related by testing a simple scene or a fresh project on the new version. If the issue follows the runtime, restore the backed-up folder into a test copy of the installation, not over your working install, and see whether the problem disappears. Testing in a copy keeps your options open.
Keep in mind that restoring an old runtime into a new editor is a diagnostic step, not a permanent fix. If the old runtime solves the problem, you have identified the cause, and the real fix is usually updating the plugin or code that depended on the old behaviour, or reporting the regression to Unity. The backup buys you time and evidence, which are the two things you need most when a build breaks unexpectedly.
What About Version Control?
A common question is whether the runtime folder belongs in version control. For most projects, the answer is no. The folder is large, it changes with every Unity update, and it can always be regenerated by installing the matching Unity version. Committing it bloats the repository and slows down every clone for no real benefit. What does belong in version control is the record of which Unity version the project uses, usually through the project’s version file, plus your backup notes about which runtime copy goes with which release. That combination gives you reproducibility without the storage cost. The exception is a project that must build in a sealed environment with no access to Unity’s download servers; in that rare case, archiving the installer or the runtime folder alongside the project is a deliberate decision, not a default.
Backing Up Built Games Too
Developers usually focus on the editor copy, but shipped builds deserve a thought as well. If you distribute a game directly, keeping an archive of each released build, including its data folder and runtime folder, lets you reproduce a player’s exact setup when they report a bug. Store builds are less of a concern, because the store keeps the released version for you, but for direct downloads and press copies, your own archive is the only record. Disk space is cheap compared with the cost of being unable to reproduce a crash that only happens in one shipped version.
Building the Habit Into Your Workflow
The easiest backup routine is the one that happens automatically. Some developers add a pre-update checklist to their project notes: close the editor, copy the runtime folder, record the version, then update. Others script the copy step so it runs with one command. Either approach works, because the goal is consistency, not sophistication.
Updates will always carry some risk, and no backup removes that risk entirely. But a backed-up runtime folder turns a potential crisis into a manageable comparison task. If you want a deeper explanation of what lives inside that folder and why it matters so much, monobleedingedge.com covers the runtime’s role in Unity’s architecture in more detail.
