diff --git a/CHDataManagement/Generator/Blocks/VideoBlock.swift b/CHDataManagement/Generator/Blocks/VideoBlock.swift
index acd88e5..8206ec4 100644
--- a/CHDataManagement/Generator/Blocks/VideoBlock.swift
+++ b/CHDataManagement/Generator/Blocks/VideoBlock.swift
@@ -188,6 +188,14 @@ extension VideoBlock {
             case .webm: "video/webm"
             }
         }
+
+        static func h265(codec: String) -> SourceType? {
+            switch codec {
+            case "hvc1": return .h265
+            case "avc1": return .h264
+            default: return nil
+            }
+        }
     }
 
     struct Source {
diff --git a/CHDataManagement/Generator/Commands/VideoCommand.swift b/CHDataManagement/Generator/Commands/VideoCommand.swift
index aade462..f990b24 100644
--- a/CHDataManagement/Generator/Commands/VideoCommand.swift
+++ b/CHDataManagement/Generator/Commands/VideoCommand.swift
@@ -30,8 +30,8 @@ struct VideoCommand: CommandProcessor {
         }
         results.require(file: file)
 
-        guard let videoType = file.type.htmlType else {
-            invalid(markdown)
+        guard let videoType = file.videoType() else {
+            invalid("File \(file.identifier) has an unknown video type")
             return ""
         }
 
diff --git a/CHDataManagement/Generator/ImageGenerator.swift b/CHDataManagement/Generator/ImageGenerator.swift
index f2a8185..abf8983 100644
--- a/CHDataManagement/Generator/ImageGenerator.swift
+++ b/CHDataManagement/Generator/ImageGenerator.swift
@@ -186,6 +186,7 @@ final class ImageGenerator {
         let generatedImagePath = storage.outputPath(to: version.outputPath)!.path()
         let quality = Int(version.quality * 100)
 
+        // TODO: Run in security scope
         let process = Process()
         #warning("TODO: Move avifenc path to settings")
         process.launchPath = "/opt/homebrew/bin/avifenc" // Adjust based on installation
diff --git a/CHDataManagement/Generator/Post Lists/PostListPageGenerator.swift b/CHDataManagement/Generator/Post Lists/PostListPageGenerator.swift
index d8dd02f..19aedac 100644
--- a/CHDataManagement/Generator/Post Lists/PostListPageGenerator.swift	
+++ b/CHDataManagement/Generator/Post Lists/PostListPageGenerator.swift	
@@ -82,7 +82,18 @@ final class PostListPageGenerator {
             images.forEach(source.results.require)
             media = .images(images)
         } else if localized.hasVideos {
-            media = .video(localized.images)
+            let videos: [PostVideo.Video] = localized.images.compactMap { file -> PostVideo.Video? in
+                guard file.type.isVideo else {
+                    self.source.results.warning("File \(file.identifier) ignored due to videos present in the post")
+                    return nil
+                }
+                guard let type = file.videoType() else {
+                    self.source.results.warning("Video \(file.identifier) ignored due to unknown video type")
+                    return nil
+                }
+                return .init(path: file.absoluteUrl, type: type)
+            }
+            media = .video(videos)
             localized.images.forEach(source.results.require)
         } else {
             media = nil
diff --git a/CHDataManagement/Model/FileResource.swift b/CHDataManagement/Model/FileResource.swift
index 23e6b8e..2d57e2b 100644
--- a/CHDataManagement/Model/FileResource.swift
+++ b/CHDataManagement/Model/FileResource.swift
@@ -343,6 +343,62 @@ final class FileResource: Item, LocalizedItem {
         }
     }
 
+    private var _videoType: String?
+
+    func videoType() -> String? {
+        if let _videoType {
+            return _videoType
+        }
+        _videoType = determineVideoType()
+        return _videoType
+    }
+
+    private func determineVideoType() -> String? {
+        #warning("TODO: Move ffmpeg path to settings")
+        switch type {
+        case .webm:
+            return "video/webm"
+        case .mp4, .m4v:
+            if isExternallyStored {
+                return "video/mp4"
+            }
+            break
+        default:
+            return nil
+        }
+
+        return content.storage.with(file: identifier) { path in
+            let process = Process()
+            let arguments = "-v error -select_streams v:0 -show_entries stream=codec_tag_string -of default=noprint_wrappers=1:nokey=1 \(path.path())"
+                .components(separatedBy: " ")
+            process.launchPath = "/opt/homebrew/bin/ffprobe"
+            process.arguments = Array(arguments)
+
+            let pipe = Pipe()
+            process.standardOutput = pipe
+            process.standardError = pipe
+
+            process.launch()
+            process.waitUntilExit()
+
+            let outputData = pipe.fileHandleForReading.readDataToEndOfFile()
+            let outputString = String(data: outputData, encoding: .utf8) ?? ""
+
+            if process.terminationStatus != 0 {
+                print("Failed to determine video type for \(identifier)")
+                print(outputString)
+                return nil
+            }
+            let firstLine = outputString.components(separatedBy: .newlines).first!.trimmed
+            guard let type = VideoBlock.SourceType.h265(codec: firstLine) else {
+                print("Unknown codec type for \(identifier): \(firstLine)")
+                print(outputString)
+                return "video/mp4"
+            }
+            return type.mimeType
+        }
+    }
+
     // MARK: Paths
 
     func removeFileFromOutputFolder() {
diff --git a/CHDataManagement/Model/FileType.swift b/CHDataManagement/Model/FileType.swift
index e6f01af..adab248 100644
--- a/CHDataManagement/Model/FileType.swift
+++ b/CHDataManagement/Model/FileType.swift
@@ -234,15 +234,4 @@ enum FileType: String {
         default: return false
         }
     }
-
-    var htmlType: String? {
-        switch self {
-        case .mp4, .m4v:
-            return "video/mp4"
-        case .webm:
-            return "video/webm"
-        default:
-            return nil
-        }
-    }
 }
diff --git a/CHDataManagement/Page Elements/ContentElements/PostVideo.swift b/CHDataManagement/Page Elements/ContentElements/PostVideo.swift
index 50cf3c9..3d8bf6c 100644
--- a/CHDataManagement/Page Elements/ContentElements/PostVideo.swift	
+++ b/CHDataManagement/Page Elements/ContentElements/PostVideo.swift	
@@ -1,13 +1,18 @@
 
 struct PostVideo: HtmlProducer {
 
-    let videos: [FileResource]
+    struct Video {
+        let path: String
+        let type: String
+    }
+
+    let videos: [Video]
 
     func populate(_ result: inout String) {
         result += "<video autoplay loop muted playsinline>"
         result += "Video not supported."
         for video in videos {
-            result += "<source src='\(video.absoluteUrl)' type='\(video.type.htmlType!)'>"
+            result += "<source src='\(video.path)' type='\(video.type)'>"
         }
         result += "</video>"
     }
diff --git a/CHDataManagement/Page Elements/FeedEntryData.swift b/CHDataManagement/Page Elements/FeedEntryData.swift
index 7a7937a..facac4d 100644
--- a/CHDataManagement/Page Elements/FeedEntryData.swift	
+++ b/CHDataManagement/Page Elements/FeedEntryData.swift	
@@ -46,7 +46,7 @@ struct FeedEntryData {
 
     enum Media {
         case images([ImageSet])
-        case video([FileResource])
+        case video([PostVideo.Video])
     }
 
     var requiresSwiper: Bool {
diff --git a/CHDataManagement/Storage/Storage.swift b/CHDataManagement/Storage/Storage.swift
index f49522d..417fdb8 100644
--- a/CHDataManagement/Storage/Storage.swift
+++ b/CHDataManagement/Storage/Storage.swift
@@ -432,6 +432,12 @@ final class Storage: ObservableObject {
         return await contentScope.with(relativePath: path, perform: operation)
     }
 
+    func with<T>(file fileId: String, perform operation: (URL) -> T?) -> T? {
+        guard let contentScope else { return nil }
+        let path = filePath(file: fileId)
+        return contentScope.with(relativePath: path, perform: operation)
+    }
+
     // MARK: Video thumbnails
 
     func hasVideoThumbnail(for videoId: String) -> Bool {