Unity asset GUIDs regenerator

UnityGuidRegenerator.cs

// Drop into Assets/Editor, use "Tools/Regenerate asset GUIDs"

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using UnityEditor;

namespace UnityGuidRegenerator {
    public class UnityGuidRegeneratorMenu {
        [MenuItem("Tools/Regenerate asset GUIDs")]
        public static void RegenerateGuids() {
            if (EditorUtility.DisplayDialog("GUIDs regeneration",
                "You are going to start the process of GUID regeneration. This may have unexpected results. \n\nMAKE A PROJECT BACKUP BEFORE PROCEEDING!",
                "Regenerate GUIDs", "Cancel")) {
                try {
                    AssetDatabase.StartAssetEditing();

                    string path = Path.GetFullPath(".") + Path.DirectorySeparatorChar + "Assets";
                    UnityGuidRegenerator regenerator = new UnityGuidRegenerator(path);
                    regenerator.RegenerateGuids();
                }
                finally {
                    AssetDatabase.StopAssetEditing();
                    EditorUtility.ClearProgressBar();
                    AssetDatabase.Refresh();
                }
            }
        }
    }

    internal class UnityGuidRegenerator {
        private static readonly string[] kDefaultFileExtensions = {
            "*.meta",
            "*.mat",
            "*.anim",
            "*.prefab",
            "*.unity",
            "*.asset",
            "*.guiskin",
            "*.fontsettings",
            "*.controller",
        };

        private readonly string _assetsPath;

        public UnityGuidRegenerator(string assetsPath) {
            _assetsPath = assetsPath;
        }

        public void RegenerateGuids(string[] regeneratedExtensions = null) {
            if (regeneratedExtensions == null) {
                regeneratedExtensions = kDefaultFileExtensions;
            }

            // Get list of working files
            List<string> filesPaths = new List<string>();
            foreach (string extension in regeneratedExtensions) {
                filesPaths.AddRange(
                    Directory.GetFiles(_assetsPath, extension, SearchOption.AllDirectories)
                    );
            }

            // Create dictionary to hold old-to-new GUID map
            Dictionary<string, string> guidOldToNewMap = new Dictionary<string, string>();
            Dictionary<string, List<string>> guidsInFileMap = new Dictionary<string, List<string>>();

            // We must only replace GUIDs for Resources present in Assets. 
            // Otherwise built-in resources (shader, meshes etc) get overwritten.
            HashSet<string> ownGuids = new HashSet<string>();

            // Traverse all files, remember which GUIDs are in which files and generate new GUIDs
            int counter = 0;
            foreach (string filePath in filesPaths) {
                if (!EditorUtility.DisplayCancelableProgressBar("Scanning Assets folder", MakeRelativePath(_assetsPath, filePath),
                    counter / (float) filesPaths.Count)) {
                    string contents = File.ReadAllText(filePath);

                    IEnumerable<string> guids = GetGuids(contents);
                    bool isFirstGuid = true;
                    foreach (string oldGuid in guids) {
                        // First GUID in .meta file is always the GUID of the asset itself
                        if (isFirstGuid && Path.GetExtension(filePath) == ".meta") {
                            ownGuids.Add(oldGuid);
                            isFirstGuid = false;
                        }
                        // Generate and save new GUID if we haven't added it before
                        if (!guidOldToNewMap.ContainsKey(oldGuid)) {
                            string newGuid = Guid.NewGuid().ToString("N");
                            guidOldToNewMap.Add(oldGuid, newGuid);
                        }

                        if (!guidsInFileMap.ContainsKey(filePath))
                            guidsInFileMap[filePath] = new List<string>();

                        if (!guidsInFileMap[filePath].Contains(oldGuid)) {
                            guidsInFileMap[filePath].Add(oldGuid);
                        }
                    }

                    counter++;
                } else {
                    UnityEngine.Debug.LogWarning("GUID regeneration canceled");
                    return;
                }
            }

            // Traverse the files again and replace the old GUIDs
            counter = -1;
            int guidsInFileMapKeysCount = guidsInFileMap.Keys.Count;
            foreach (string filePath in guidsInFileMap.Keys) {
                EditorUtility.DisplayProgressBar("Regenerating GUIDs", MakeRelativePath(_assetsPath, filePath), counter / (float) guidsInFileMapKeysCount);
                counter++;

                string contents = File.ReadAllText(filePath);
                foreach (string oldGuid in guidsInFileMap[filePath]) {
                    if (!ownGuids.Contains(oldGuid))
                        continue;

                    string newGuid = guidOldToNewMap[oldGuid];
                    if (string.IsNullOrEmpty(newGuid))
                        throw new NullReferenceException("newGuid == null");

                    contents = contents.Replace("guid: " + oldGuid, "guid: " + newGuid);
                }
                File.WriteAllText(filePath, contents);
            }

            EditorUtility.ClearProgressBar();
        }

        private static IEnumerable<string> GetGuids(string text) {
            const string guidStart = "guid: ";
            const int guidLength = 32;
            int textLength = text.Length;
            int guidStartLength = guidStart.Length;
            List<string> guids = new List<string>();

            int index = 0;
            while (index + guidStartLength + guidLength < textLength) {
                index = text.IndexOf(guidStart, index, StringComparison.Ordinal);
                if (index == -1)
                    break;

                index += guidStartLength;
                string guid = text.Substring(index, guidLength);
                index += guidLength;

                if (IsGuid(guid)) {
                    guids.Add(guid);
                }
            }

            return guids;
        }

        private static bool IsGuid(string text) {
            for (int i = 0; i < text.Length; i++) {
                char c = text[i];
                if (
                    !((c >= '0' && c <= '9') ||
                      (c >= 'a' && c <= 'z'))
                    )
                    return false;
            }

            return true;
        }

        private static string MakeRelativePath(string fromPath, string toPath) {
            Uri fromUri = new Uri(fromPath);
            Uri toUri = new Uri(toPath);

            Uri relativeUri = fromUri.MakeRelativeUri(toUri);
            string relativePath = Uri.UnescapeDataString(relativeUri.ToString());

            return relativePath;
        }
    }
}

It works like a charm! I though it wasn't going to change guids also in .unity data, but it was!
We are merging multiple projects that contains some shared assets with same guids :(

You have saved us tons of hours

Appreciated. Hacked on it to update UMA Overlay Guids. Very helpful.

I had issues using this with the latest version of Unity on Windows. Unity now marks .meta files as hidden which causes File.WriteAllText to throw an authorization exception when trying to write to them. The solution I found was to use stream writing instead and replace:
File.WriteAllText(filePath, contents);
with:
using (FileStream fs = new FileStream(filePath, FileMode.Open)) { using (TextWriter tw = new StreamWriter(fs, Encoding.UTF8, 1024, true)) { tw.Write(contents); } fs.SetLength(fs.Position); }
(Apologies for terrible formatting)
The issue appears to be that File.WriteAllText performs an implicit File.Exists style check which fails on hidden files. Using streams directly gets around that check.

@ZimM-LostPolygon, thanks for sharing this wonderful and helpful script.

I had issues using this with the latest version of Unity on Windows. Unity now marks .meta files as hidden which causes File.WriteAllText to throw an authorization exception when trying to write to them. The solution I found was to use stream writing instead and replace:
File.WriteAllText(filePath, contents);
with:
using (FileStream fs = new FileStream(filePath, FileMode.Open)) { using (TextWriter tw = new StreamWriter(fs, Encoding.UTF8, 1024, true)) { tw.Write(contents); } fs.SetLength(fs.Position); }
(Apologies for terrible formatting)
The issue appears to be that File.WriteAllText performs an implicit File.Exists style check which fails on hidden files. Using streams directly gets around that check.

@geolands, I faced this same issue and using FileStream solved it. Thanks a ton for sharing the issue and the solution along with it. :)

I'm facing an issue where after running this script, Unity scenes complain that their scripts cannot be found.

Hi, my projects do not have the route Assets/Editor, where it is supposed to be copied this script into my project?

@famo

Hi, my projects do not have the route Assets/Editor, where it is supposed to be copied this script into my project?

You just create the folder if it does not exist and then put it in there. Right-click in the project => Create new folder => name it Editor.

I found my unity project at 2019.4.0f1 Guid didn't have alphabet characters bigger and equal to 'g'.
Maybe it doesn't have to check Guid character from g to z, in the function of IsGuid(string text).

From

        private static bool IsGuid(string text)
        {
            for (int i = 0; i < text.Length; i++)
            {
                char c = text[i];
                if (
                    !((c >= '0' && c <= '9') ||
                      (c >= 'a' && c <= 'z'))
                    )
                    return false;
            }

            return true;
        }

to

        private static bool IsGuid(string text)
        {
            for (int i = 0; i < text.Length; i++)
            {
                char c = text[i];
                if (
                    !((c >= '0' && c <= '9') ||
                      (c >= 'a' && c <= 'f'))
                    )
                    return false;
            }

            return true;
        }

need assembly definition implementation. asmdef didn't be replaced to new guid

THAAAAAAAAAAAAAAAAAAANKKSSSSSSSSSSSSSSSSSSSSSSSSSS !!!!!!!!!!!!!!!!!!!

Still works as expected in Unity 2021 👍

I'm facing an issue where after running this script, Unity scenes complain that their scripts cannot be found . Unity version 2021.3.11f

Perfect!! It worked for me. Thanks a lot!

Thanks for sharing this.