diff --git a/src/main/kotlin/io/github/sculk_cli/commands/AddByUrl.kt b/src/main/kotlin/io/github/sculk_cli/commands/AddByUrl.kt
index 5f411fc..b5505a9 100644
--- a/src/main/kotlin/io/github/sculk_cli/commands/AddByUrl.kt
+++ b/src/main/kotlin/io/github/sculk_cli/commands/AddByUrl.kt
@@ -45,21 +45,18 @@ class AddByUrl :
         }
 
         val existingManifest = ctx.pack.getManifest("$dir/$transformedSlug.sculk.json")
+        val hashes = FileManifestHashes(
+            sha1 = contents.digestSha1(),
+            sha512 = contents.digestSha512(),
+            murmur2 = contents.digestMurmur2()
+        )
         val fileManifest = if (existingManifest != null) {
-            if (existingManifest.hashes.sha1 != contents.digestSha1() || existingManifest.hashes.sha512 != contents.digestSha512()) {
-                error("File hashes do not match for $filename")
-            }
-
-            existingManifest.sources.url = FileManifestUrlSource(url.toString())
+            existingManifest.sources.url = FileManifestUrlSource(url.toString(), hashes)
             existingManifest
         } else {
 	        FileManifest(
-		        filename = filename, side = side, hashes = FileManifestHashes(
-			        sha1 = contents.digestSha1(),
-			        sha512 = contents.digestSha512(),
-			        murmur2 = contents.digestMurmur2()
-		        ), fileSize = contents.size, sources = FileManifestSources(
-			        curseforge = null, modrinth = null, url = FileManifestUrlSource(url.toString())
+		        filename = filename, side = side, fileSize = contents.size, sources = FileManifestSources(
+			        curseforge = null, modrinth = null, url = FileManifestUrlSource(url.toString(), hashes)
 		        )
 	        )
         }
diff --git a/src/main/kotlin/io/github/sculk_cli/commands/ExportModrinth.kt b/src/main/kotlin/io/github/sculk_cli/commands/ExportModrinth.kt
index bed6fe3..1021f47 100644
--- a/src/main/kotlin/io/github/sculk_cli/commands/ExportModrinth.kt
+++ b/src/main/kotlin/io/github/sculk_cli/commands/ExportModrinth.kt
@@ -13,6 +13,7 @@ import io.github.sculk_cli.util.toModrinthEnvClientSupport
 import io.github.sculk_cli.util.toModrinthEnvServerSupport
 import io.github.sculk_cli.modrinth.*
 import io.github.sculk_cli.modrinth.models.ModrinthVersionFileHashes
+import io.github.sculk_cli.pack.FileManifestHashes
 import java.io.File
 import java.nio.file.Paths
 
@@ -42,13 +43,16 @@ class ExportModrinth :
 
         for ((path, fileManifest) in ctx.pack.getManifests().entries) {
             val downloadUrls = mutableListOf<String>()
+            var hashes: FileManifestHashes? = null
 
             if (fileManifest.sources.modrinth != null) {
                 downloadUrls += fileManifest.sources.modrinth!!.fileUrl
+                hashes = fileManifest.sources.modrinth!!.hashes
             }
 
             if (fileManifest.sources.url != null) {
                 downloadUrls += fileManifest.sources.url!!.url
+                hashes = hashes ?: fileManifest.sources.url!!.hashes
             }
 
             val filteredDownloadUrls = downloadUrls
@@ -61,11 +65,16 @@ class ExportModrinth :
                 continue
             }
 
+            if (hashes == null) {
+                terminal.warning("File $path will not be included as it does not have hashes")
+                continue
+            }
+
             files += ModrinthPackFile(
                 path = File(path).resolveSibling(fileManifest.filename).toString(),
                 hashes = ModrinthVersionFileHashes(
-                    sha1 = fileManifest.hashes.sha1,
-                    sha512 = fileManifest.hashes.sha512
+                    sha1 = hashes.sha1,
+                    sha512 = hashes.sha512
                 ),
                 env = ModrinthPackFileEnv(
                     clientSupport = fileManifest.side.toModrinthEnvClientSupport(),
diff --git a/src/main/kotlin/io/github/sculk_cli/commands/ImportCurseforge.kt b/src/main/kotlin/io/github/sculk_cli/commands/ImportCurseforge.kt
index 5a358c8..6c19744 100644
--- a/src/main/kotlin/io/github/sculk_cli/commands/ImportCurseforge.kt
+++ b/src/main/kotlin/io/github/sculk_cli/commands/ImportCurseforge.kt
@@ -96,17 +96,17 @@ class ImportCurseforge :
                 val fileManifest = FileManifest(
 	                filename = cfFile.fileName,
 	                side = cfFile.getSide().toSide(),
-	                hashes = FileManifestHashes(
-		                sha1 = tempFile.digestSha1(),
-		                sha512 = tempFile.digestSha512(),
-		                murmur2 = tempFile.digestMurmur2()
-	                ),
 	                fileSize = tempFile.size,
 	                sources = FileManifestSources(
 		                curseforge = FileManifestCurseforgeSource(
 			                projectId = mod.id,
 			                fileId = file.fileId,
-			                fileUrl = cfFile.downloadUrl!!
+			                fileUrl = cfFile.downloadUrl!!,
+                            hashes = FileManifestHashes(
+                                sha1 = tempFile.digestSha1(),
+                                sha512 = tempFile.digestSha512(),
+                                murmur2 = tempFile.digestMurmur2()
+                            ),
 		                ),
 		                modrinth = null,
 		                url = null
diff --git a/src/main/kotlin/io/github/sculk_cli/commands/ImportModrinth.kt b/src/main/kotlin/io/github/sculk_cli/commands/ImportModrinth.kt
index 6762ee8..dd5e775 100644
--- a/src/main/kotlin/io/github/sculk_cli/commands/ImportModrinth.kt
+++ b/src/main/kotlin/io/github/sculk_cli/commands/ImportModrinth.kt
@@ -35,6 +35,8 @@ import io.github.sculk_cli.util.toModLoader
 import io.github.sculk_cli.util.toSide
 import io.github.sculk_cli.modrinth.getLoaderVersionPair
 import io.github.sculk_cli.modrinth.importModrinthPack
+import io.github.sculk_cli.util.digestSha1
+import io.github.sculk_cli.util.digestSha512
 import java.io.File
 import java.nio.file.Paths
 import kotlin.collections.plusAssign
@@ -75,11 +77,6 @@ class ImportModrinth :
                 val fileManifest = FileManifest(
 	                filename = File(file.path).name,
 	                side = file.env?.toSide() ?: Side.Both,
-	                hashes = FileManifestHashes(
-		                sha1 = file.hashes.sha1,
-		                sha512 = file.hashes.sha512,
-		                murmur2 = -1, // Updated later in the loop
-	                ),
 	                fileSize = file.fileSizeInBytes,
 	                sources = FileManifestSources(
 		                curseforge = null,
@@ -93,14 +90,14 @@ class ImportModrinth :
                 for (downloadUrl in file.downloadUrls) {
                     progress.advance(1)
                     progress.update { context = downloadUrl }
-
-                    if (fileManifest.hashes.murmur2 == -1L) {
-                        val file = downloadFileTemp(parseUrl(downloadUrl))
-                        fileManifest.hashes.murmur2 = file.readBytes().digestMurmur2()
-                    }
+                    val file = downloadFileTemp(parseUrl(downloadUrl))
+                    val bytes = file.readBytes()
+                    val sha1 = bytes.digestSha1()
+                    val sha512 = bytes.digestSha512()
+                    val murmur2 = bytes.digestMurmur2()
 
                     if (parseUrl(downloadUrl).host == "cdn.modrinth.com") {
-                        val version = ctx.modrinth.getVersionFromHash(file.hashes.sha1)
+                        val version = ctx.modrinth.getVersionFromHash(sha1)
                             ?: run {
                                 terminal.warning("File ${file.path} includes a Modrinth file that does not seem to exist")
                                 null
@@ -108,12 +105,21 @@ class ImportModrinth :
 
                         fileManifest.sources.modrinth = FileManifestModrinthSource(
 	                        projectId = version.projectId,
-	                        fileUrl = downloadUrl
+	                        fileUrl = downloadUrl,
+                            hashes = FileManifestHashes(
+                                sha1 = sha1,
+                                sha512 = sha512,
+                                murmur2 = murmur2,
+                            ),
                         )
 
                         slug = ctx.modrinth.getProject(version.projectId)!!.slug
                     } else if (fileManifest.sources.url == null) {
-                        fileManifest.sources.url = FileManifestUrlSource(downloadUrl)
+                        fileManifest.sources.url = FileManifestUrlSource(downloadUrl, FileManifestHashes(
+                            sha1 = sha1,
+                            sha512 = sha512,
+                            murmur2 = murmur2,
+                        ))
                     } else {
                         terminal.warning("File ${file.path} has multiple valid URL sources; only the first will be included")
                     }
diff --git a/src/main/kotlin/io/github/sculk_cli/commands/Install.kt b/src/main/kotlin/io/github/sculk_cli/commands/Install.kt
index ace0482..50d7cd4 100644
--- a/src/main/kotlin/io/github/sculk_cli/commands/Install.kt
+++ b/src/main/kotlin/io/github/sculk_cli/commands/Install.kt
@@ -102,13 +102,6 @@ class Install :
 
                     installedItems += fileFile.path.toString()
 
-                    if (fileFile.exists()) {
-                        if (fileFile.readBytes().digestSha512() == fileManifest.hashes.sha512) {
-                            terminal.info("Skipping ${file.path} because it's already downloaded")
-                            return@launch
-                        }
-                    }
-
                     val downloadLink = if (fileManifest.sources.url != null) {
                         fileManifest.sources.url.url
                     } else if (fileManifest.sources.modrinth != null) {
@@ -119,6 +112,23 @@ class Install :
                         error("No valid source found for ${file.path}")
                     }
 
+                    val hashes = if (fileManifest.sources.url != null) {
+                        fileManifest.sources.url.hashes
+                    } else if (fileManifest.sources.modrinth != null) {
+                        fileManifest.sources.modrinth.hashes
+                    } else if (fileManifest.sources.curseforge != null) {
+                        fileManifest.sources.curseforge.hashes
+                    } else {
+                        error("No valid hashes found for ${file.path}")
+                    }
+
+                    if (fileFile.exists()) {
+                        if (fileFile.readBytes().digestSha512() == hashes.sha512) {
+                            terminal.info("Skipping ${file.path} because it's already downloaded")
+                            return@launch
+                        }
+                    }
+
                     fileFile.parentFile.mkdirs()
                     val request = ctx.client.get(downloadLink) {
                         timeout {
@@ -128,7 +138,7 @@ class Install :
                     }
                     fileFile.writeBytes(request.readRawBytes())
 
-                    if (fileFile.readBytes().digestSha512() != fileManifest.hashes.sha512) {
+                    if (fileFile.readBytes().digestSha512() != hashes.sha512) {
                         error("Downloaded file for ${file.path} was corrupted or hash was incorrect")
                     }
 
diff --git a/src/main/kotlin/io/github/sculk_cli/commands/Link.kt b/src/main/kotlin/io/github/sculk_cli/commands/Link.kt
index 3aa1686..aa7cecb 100644
--- a/src/main/kotlin/io/github/sculk_cli/commands/Link.kt
+++ b/src/main/kotlin/io/github/sculk_cli/commands/Link.kt
@@ -55,9 +55,19 @@ class Link : CliktCommand(
 	    ctx: Context,
 	    manifest: Map.Entry<String, FileManifest>
     ) {
+        val hashes = if (manifest.value.sources.url != null) {
+            manifest.value.sources.url!!.hashes
+        } else if (manifest.value.sources.modrinth != null) {
+            manifest.value.sources.modrinth!!.hashes
+        } else if (manifest.value.sources.curseforge != null) {
+            manifest.value.sources.curseforge!!.hashes
+        } else {
+            error("No valid hashes found for ${manifest.key}")
+        }
+
         when (target) {
             Target.Curseforge -> {
-                val matches = ctx.curseforge.getFingerprintMatches(manifest.value.hashes.murmur2)
+                val matches = ctx.curseforge.getFingerprintMatches(hashes.murmur2)
 
                 if (matches.isEmpty()) {
                     terminal.info("No match found for ${manifest.key}")
@@ -85,7 +95,7 @@ class Link : CliktCommand(
 
             Target.Modrinth -> {
                 val version = ctx.modrinth.getVersionFromHash(
-                    manifest.value.hashes.sha512,
+                    hashes.sha512,
                     ModrinthHashAlgorithm.SHA512
                 )
 
diff --git a/src/main/kotlin/io/github/sculk_cli/pack/InMemory.kt b/src/main/kotlin/io/github/sculk_cli/pack/InMemory.kt
index 82abe82..a13b20e 100644
--- a/src/main/kotlin/io/github/sculk_cli/pack/InMemory.kt
+++ b/src/main/kotlin/io/github/sculk_cli/pack/InMemory.kt
@@ -173,7 +173,6 @@ data class PackManifestFile(
 data class FileManifest(
     var filename: String,
     var side: Side,
-    var hashes: FileManifestHashes,
     var fileSize: Int,
     var sources: FileManifestSources
 )
@@ -189,15 +188,15 @@ data class FileManifestSources(
 )
 
 data class FileManifestCurseforgeSource(
-    var projectId: Int, var fileUrl: String, var fileId: Int,
+    var projectId: Int, var fileUrl: String, var fileId: Int, var hashes: FileManifestHashes,
 )
 
 data class FileManifestModrinthSource(
-    var projectId: String, var fileUrl: String,
+    var projectId: String, var fileUrl: String, var hashes: FileManifestHashes,
 )
 
 data class FileManifestUrlSource(
-    var url: String
+    var url: String, var hashes: FileManifestHashes,
 )
 
 fun PackManifest.toSerial(): SerialPackManifest {
@@ -232,11 +231,6 @@ fun FileManifest.toSerial(): SerialFileManifest {
     return SerialFileManifest(
         filename = filename,
         side = side,
-        hashes = SerialFileManifestHashes(
-            sha1 = hashes.sha1,
-            sha512 = hashes.sha512,
-            murmur2 = hashes.murmur2,
-        ),
         fileSize = fileSize,
         sources = SerialFileManifestSources(
             curseforge = sources.curseforge?.let {
@@ -244,19 +238,30 @@ fun FileManifest.toSerial(): SerialFileManifest {
                     projectId = it.projectId,
                     fileUrl = it.fileUrl,
                     fileId = it.fileId,
+                    hashes = it.hashes.toSerial(),
                 )
             },
             modrinth = sources.modrinth?.let {
                 SerialFileManifestModrinthSource(
                     projectId = it.projectId,
                     fileUrl = it.fileUrl,
+                    hashes = it.hashes.toSerial(),
                 )
             },
             url = sources.url?.let {
                 SerialFileManifestUrlSource(
                     url = it.url,
+                    hashes = it.hashes.toSerial(),
                 )
             },
         )
     )
 }
+
+fun FileManifestHashes.toSerial(): SerialFileManifestHashes {
+    return SerialFileManifestHashes(
+        sha1 = sha1,
+        sha512 = sha512,
+        murmur2 = murmur2,
+    )
+}
diff --git a/src/main/kotlin/io/github/sculk_cli/pack/Serial.kt b/src/main/kotlin/io/github/sculk_cli/pack/Serial.kt
index 47635de..964888e 100644
--- a/src/main/kotlin/io/github/sculk_cli/pack/Serial.kt
+++ b/src/main/kotlin/io/github/sculk_cli/pack/Serial.kt
@@ -36,7 +36,6 @@ data class SerialPackManifestFile(
 data class SerialFileManifest(
     val filename: String,
     val side: Side,
-    val hashes: SerialFileManifestHashes,
     val fileSize: Int,
     val sources: SerialFileManifestSources
 )
@@ -55,17 +54,17 @@ data class SerialFileManifestSources(
 
 @Serializable
 data class SerialFileManifestCurseforgeSource(
-    val projectId: Int, val fileUrl: String, val fileId: Int,
+    val projectId: Int, val fileUrl: String, val fileId: Int, val hashes: SerialFileManifestHashes,
 )
 
 @Serializable
 data class SerialFileManifestModrinthSource(
-    val projectId: String, val fileUrl: String,
+    val projectId: String, val fileUrl: String, val hashes: SerialFileManifestHashes,
 )
 
 @Serializable
 data class SerialFileManifestUrlSource(
-    var url: String
+    var url: String, val hashes: SerialFileManifestHashes,
 )
 
 fun SerialPackManifest.load(): PackManifest {
@@ -98,29 +97,36 @@ fun SerialPackManifest.load(): PackManifest {
 
 fun SerialFileManifest.load(): FileManifest {
     return FileManifest(
-        filename = filename, side = side, hashes = FileManifestHashes(
-            sha1 = hashes.sha1,
-            sha512 = hashes.sha512,
-            murmur2 = hashes.murmur2,
-        ), fileSize = fileSize, sources = FileManifestSources(
+        filename = filename, side = side, fileSize = fileSize, sources = FileManifestSources(
             curseforge = sources.curseforge?.let {
                 FileManifestCurseforgeSource(
                     projectId = it.projectId,
                     fileUrl = it.fileUrl,
                     fileId = it.fileId,
+                    hashes = it.hashes.load(),
                 )
             },
             modrinth = sources.modrinth?.let {
                 FileManifestModrinthSource(
                     projectId = it.projectId,
                     fileUrl = it.fileUrl,
+                    hashes = it.hashes.load(),
                 )
             },
             url = sources.url?.let {
                 FileManifestUrlSource(
                     url = it.url,
+                    hashes = it.hashes.load(),
                 )
             },
         )
     )
 }
+
+fun SerialFileManifestHashes.load(): FileManifestHashes {
+    return FileManifestHashes(
+        sha1 = sha1,
+        sha512 = sha512,
+        murmur2 = murmur2,
+    )
+}
diff --git a/src/main/kotlin/io/github/sculk_cli/util/CurseforgeUtil.kt b/src/main/kotlin/io/github/sculk_cli/util/CurseforgeUtil.kt
index 2110c8e..025c2ff 100644
--- a/src/main/kotlin/io/github/sculk_cli/util/CurseforgeUtil.kt
+++ b/src/main/kotlin/io/github/sculk_cli/util/CurseforgeUtil.kt
@@ -120,25 +120,19 @@ suspend fun addCurseforgeFile(
             error("Existing manifest already has a Curseforge source (did you mean to use the update command?)")
         }
 
-        if (existingManifest.hashes.sha1 != sha1 || existingManifest.hashes.sha512 != sha512) {
-            error("File hashes do not match for ${file.fileName}")
-        }
-
         existingManifest.sources.curseforge = FileManifestCurseforgeSource(
-	        projectId = mod.id, fileUrl = file.downloadUrl!!, fileId = file.id
+	        projectId = mod.id, fileUrl = file.downloadUrl!!, fileId = file.id, hashes = FileManifestHashes(sha1, sha512, murmur2)
         )
 
         existingManifest
     } else {
 	    FileManifest(
-		    filename = file.fileName, hashes = FileManifestHashes(
-			    sha1 = sha1, sha512 = sha512, murmur2 = murmur2
-		    ),
+		    filename = file.fileName,
 		    fileSize = tempFile.size,
 		    side = file.getSide().toSide(),
 		    sources = FileManifestSources(
 			    curseforge = FileManifestCurseforgeSource(
-				    projectId = mod.id, fileUrl = file.downloadUrl!!, fileId = file.id
+				    projectId = mod.id, fileUrl = file.downloadUrl!!, fileId = file.id, hashes = FileManifestHashes(sha1, sha512, murmur2)
 			    ), modrinth = null, url = null
 		    )
 	    )
@@ -242,13 +236,11 @@ suspend fun updateCurseforgeProject(
     }
 
     val tempFile = downloadFileTemp(parseUrl(file.downloadUrl!!)).readBytes()
-    manifest.hashes.sha1 = tempFile.digestSha1()
-    manifest.hashes.sha512 = tempFile.digestSha512()
     manifest.fileSize = tempFile.size
     manifest.filename = file.fileName
 
     manifest.sources.curseforge = FileManifestCurseforgeSource(
-	    projectId = mod.id, fileUrl = file.downloadUrl!!, fileId = file.id
+	    projectId = mod.id, fileUrl = file.downloadUrl!!, fileId = file.id, hashes = FileManifestHashes(tempFile.digestSha1(), tempFile.digestSha512(), tempFile.digestMurmur2())
     )
 
     return true
diff --git a/src/main/kotlin/io/github/sculk_cli/util/ModrinthUtil.kt b/src/main/kotlin/io/github/sculk_cli/util/ModrinthUtil.kt
index b981a46..a69392e 100644
--- a/src/main/kotlin/io/github/sculk_cli/util/ModrinthUtil.kt
+++ b/src/main/kotlin/io/github/sculk_cli/util/ModrinthUtil.kt
@@ -83,6 +83,7 @@ suspend fun addModrinthVersion(
 ): Boolean {
     val modrinthFile = version.files.first { it.primary }
     val tempFile = downloadFileTemp(parseUrl(modrinthFile.downloadUrl))
+    val bytes = tempFile.readBytes()
     val dir = version.loaders.first().getSaveDir()
 
     val path = manifestPath ?: "$dir/${project.slug}.sculk.json"
@@ -96,26 +97,22 @@ suspend fun addModrinthVersion(
             error("Existing manifest already has a Modrinth source (did you mean to use the update command?)")
         }
 
-        if (existingManifest.hashes.sha1 != modrinthFile.hashes.sha1 || existingManifest.hashes.sha512 != modrinthFile.hashes.sha512) {
-            error("File hashes do not match for ${modrinthFile.filename}")
-        }
-
         existingManifest.sources.modrinth = FileManifestModrinthSource(
-	        projectId = project.id, fileUrl = modrinthFile.downloadUrl
+	        projectId = project.id, fileUrl = modrinthFile.downloadUrl, hashes = FileManifestHashes(modrinthFile.hashes.sha1, modrinthFile.hashes.sha512, bytes.digestMurmur2())
         )
 
         existingManifest
     } else {
 	    FileManifest(
-		    filename = modrinthFile.filename, hashes = FileManifestHashes(
-			    sha1 = modrinthFile.hashes.sha1,
-			    sha512 = modrinthFile.hashes.sha512,
-			    murmur2 = tempFile.readBytes().digestMurmur2()
-		    ), fileSize = tempFile.readBytes().size, side = modrinthEnvTypePairToSide(
+		    filename = modrinthFile.filename, fileSize = tempFile.readBytes().size, side = modrinthEnvTypePairToSide(
 			    project.clientSideSupport, project.serverSideSupport
 		    ), sources = FileManifestSources(
 			    curseforge = null, modrinth = FileManifestModrinthSource(
-				    projectId = project.id, fileUrl = modrinthFile.downloadUrl
+				    projectId = project.id, fileUrl = modrinthFile.downloadUrl, hashes = FileManifestHashes(
+                        sha1 = modrinthFile.hashes.sha1,
+                        sha512 = modrinthFile.hashes.sha512,
+                        murmur2 = bytes.digestMurmur2()
+                    ),
 			    ), url = null
 		    )
 	    )
@@ -203,13 +200,11 @@ suspend fun updateModrinthProject(
     }
 
     val tempFile = downloadFileTemp(parseUrl(file.downloadUrl)).readBytes()
-    manifest.hashes.sha1 = tempFile.digestSha1()
-    manifest.hashes.sha512 = tempFile.digestSha512()
     manifest.fileSize = tempFile.size
     manifest.filename = file.filename
 
     manifest.sources.modrinth = FileManifestModrinthSource(
-	    projectId = mod.id, fileUrl = file.downloadUrl
+	    projectId = mod.id, fileUrl = file.downloadUrl, hashes = FileManifestHashes(tempFile.digestSha1(), tempFile.digestSha512(), tempFile.digestMurmur2())
     )
 
     return true