diff --git a/Sources/Publish/API/Mutations.swift b/Sources/Publish/API/Mutations.swift
index 738133bd..cf88f40f 100644
--- a/Sources/Publish/API/Mutations.swift
+++ b/Sources/Publish/API/Mutations.swift
@@ -6,3 +6,8 @@
 
 /// Closure type used to implement content mutations.
 public typealias Mutations<T> = (inout T) throws -> Void
+public typealias HTMLIndexMutation<Site:Website> = (PublishingContext<Site>, String) throws -> String
+public typealias HTMLSectionMutation<Site:Website> = (PublishingContext<Site>, Section<Site>, String) throws -> String
+public typealias HTMLItemMutation<Site:Website> = (PublishingContext<Site>, Item<Site>, String) throws -> String
+public typealias HTMLPageMutation<Site:Website> = (PublishingContext<Site>, Page, String) throws -> String
+public typealias HTMLAllMutation<Site:Website> = (PublishingContext<Site>, Location, String) throws -> String
diff --git a/Sources/Publish/API/PublishingContext.swift b/Sources/Publish/API/PublishingContext.swift
index 4dd14caa..ee3937a1 100644
--- a/Sources/Publish/API/PublishingContext.swift
+++ b/Sources/Publish/API/PublishingContext.swift
@@ -34,6 +34,8 @@ public struct PublishingContext<Site: Website> {
     /// Any date when the website was last generated.
     public private(set) var lastGenerationDate: Date?
 
+    internal var htmlMutations = HTMLMutations<Site>()
+
     private let folders: Folder.Group
     private var tagCache = TagCache()
     private var stepName: String
@@ -273,6 +275,27 @@ public extension PublishingContext {
             )
         }
     }
+
+    mutating func mutateIndexHTML(using mutation: @escaping HTMLIndexMutation<Site>) {
+        self.htmlMutations.indexMutations.append(mutation)
+    }
+
+    mutating func mutateSectionHTML(using mutation: @escaping HTMLSectionMutation<Site>) {
+        self.htmlMutations.sectionMutations.append(mutation)
+    }
+
+    mutating func mutateItemHTML(using mutation: @escaping HTMLItemMutation<Site>) {
+        self.htmlMutations.itemMutations.append(mutation)
+    }
+
+    mutating func mutatePageHTML(using mutation: @escaping HTMLPageMutation<Site>) {
+        self.htmlMutations.pageMutations.append(mutation)
+    }
+
+    mutating func mutateAllHTML(using mutation: @escaping HTMLAllMutation<Site>) {
+        self.htmlMutations.allMutations.append(mutation)
+    }
+
 }
 
 internal extension PublishingContext {
diff --git a/Sources/Publish/API/PublishingStep.swift b/Sources/Publish/API/PublishingStep.swift
index ecd19dbe..40f798c1 100644
--- a/Sources/Publish/API/PublishingStep.swift
+++ b/Sources/Publish/API/PublishingStep.swift
@@ -227,6 +227,39 @@ public extension PublishingStep {
         }
     }
 
+    static func mutateIndexHTML(using mutation: @escaping HTMLIndexMutation<Site>) -> Self {
+        step(named: "Mutate Index HTML") { context in
+            context.mutateIndexHTML(using: mutation)
+        }
+    }
+
+    static func mutateSectionHTML(using mutation: @escaping HTMLSectionMutation<Site>) -> Self {
+        step(named: "Mutate Section HTML") { context in
+            context.mutateSectionHTML(using: mutation)
+        }
+    }
+
+    static func mutateItemHTML(using mutation: @escaping HTMLItemMutation<Site>) -> Self {
+        step(named: "Mutate Item HTML") { context in
+            context.mutateItemHTML(using: mutation)
+        }
+    }
+
+    static func mutatePageHTML(using mutation: @escaping HTMLPageMutation<Site>) -> Self {
+        step(named: "Mutate Page HTML") { context in
+            context.mutatePageHTML(using: mutation)
+        }
+    }
+
+    static func mutateAllHTML(using mutation: @escaping HTMLAllMutation<Site>) -> Self {
+        step(named: "Mutate All HTML") { context in
+            context.mutateAllHTML(using: mutation)
+        }
+    }
+
+
+
+
     /// Sort all items, optionally within a specific section, using a key path.
     /// - parameter section: Any specific section to sort all items within.
     /// - parameter keyPath: The key path to use when sorting.
diff --git a/Sources/Publish/Internal/HTMLGenerator.swift b/Sources/Publish/Internal/HTMLGenerator.swift
index b9c69baa..d8b91a0c 100644
--- a/Sources/Publish/Internal/HTMLGenerator.swift
+++ b/Sources/Publish/Internal/HTMLGenerator.swift
@@ -48,7 +48,9 @@ private extension HTMLGenerator {
     func generateIndexHTML() throws {
         let html = try theme.makeIndexHTML(context.index, context)
         let indexFile = try context.createOutputFile(at: "index.html")
-        try indexFile.write(html.render(indentedBy: indentation))
+        var renderedHtml = html.render(indentedBy: indentation)
+        renderedHtml = try context.htmlMutations.mutateHtml(context: context, renderedHtml: renderedHtml)
+        try indexFile.write(renderedHtml)
     }
 
     func generateSectionHTML() throws {
@@ -122,16 +124,34 @@ private extension HTMLGenerator {
         }
     }
 
+    func renderHTML<T: Location>(
+        for location: T,
+        indentedBy indentation: Indentation.Kind?,
+        using generator: (T, PublishingContext<Site>) throws -> HTML
+    ) throws -> String {
+        let html = try generator(location, context)
+        return html.render(indentedBy: indentation)
+    }
+
     func outputHTML<T: Location>(
         for location: T,
         indentedBy indentation: Indentation.Kind?,
         using generator: (T, PublishingContext<Site>) throws -> HTML,
         fileMode: HTMLFileMode
     ) throws {
-        let html = try generator(location, context)
+        var renderedHtml = try renderHTML(for: location, indentedBy: indentation, using: generator)
+        if let section = location as? Section<Site> {
+            renderedHtml = try context.htmlMutations.mutateHtml(context: context, section: section, renderedHtml: renderedHtml)
+        } else if let item = location as? Item<Site> {
+            renderedHtml = try context.htmlMutations.mutateHtml(context: context, item: item, renderedHtml: renderedHtml)
+        } else if let page = location as? Page {
+            renderedHtml = try context.htmlMutations.mutateHtml(context: context, page: page, renderedHtml: renderedHtml)
+        } else {
+            renderedHtml = try context.htmlMutations.mutateHtml(context: context, location: location, renderedHtml: renderedHtml)
+        }
         let path = filePath(for: location, fileMode: fileMode)
         let file = try context.createOutputFile(at: path)
-        try file.write(html.render(indentedBy: indentation))
+        try file.write(renderedHtml)
     }
 
     func filePath(for location: Location, fileMode: HTMLFileMode) -> Path {
@@ -143,3 +163,4 @@ private extension HTMLGenerator {
         }
     }
 }
+
diff --git a/Sources/Publish/Internal/HTMLMutations.swift b/Sources/Publish/Internal/HTMLMutations.swift
new file mode 100644
index 00000000..2e7229f0
--- /dev/null
+++ b/Sources/Publish/Internal/HTMLMutations.swift
@@ -0,0 +1,58 @@
+import Plot
+
+internal struct HTMLMutations<Site: Website> {
+    var indexMutations: [HTMLIndexMutation<Site>] = []
+    var sectionMutations: [HTMLSectionMutation<Site>] = []
+    var itemMutations: [HTMLItemMutation<Site>] = []
+    var pageMutations: [HTMLPageMutation<Site>] = []
+    var allMutations: [HTMLAllMutation<Site>] = []
+
+    public init() {
+    }
+
+    func mutateHtml(context: PublishingContext<Site>, renderedHtml: String) throws -> String {
+        var mutatedHtml = renderedHtml
+        for mutation in indexMutations {
+            mutatedHtml = try mutation(context, mutatedHtml)
+        }
+        mutatedHtml = try mutateHtml(context: context, location: context.index, renderedHtml: mutatedHtml)
+        return mutatedHtml
+    }
+
+    func mutateHtml(context: PublishingContext<Site>, section: Section<Site>, renderedHtml: String) throws -> String {
+        var mutatedHtml = renderedHtml
+        for mutation in sectionMutations {
+            mutatedHtml = try mutation(context, section, mutatedHtml)
+        }
+        mutatedHtml = try mutateHtml(context: context, location: section, renderedHtml: mutatedHtml)
+        return mutatedHtml
+    }
+
+    func mutateHtml(context: PublishingContext<Site>, item: Item<Site>, renderedHtml: String) throws -> String {
+        var mutatedHtml = renderedHtml
+        for mutation in itemMutations {
+            mutatedHtml = try mutation(context, item, mutatedHtml)
+        }
+        mutatedHtml = try mutateHtml(context: context, location: item, renderedHtml: mutatedHtml)
+        return mutatedHtml
+    }
+
+    func mutateHtml(context: PublishingContext<Site>, page: Page, renderedHtml: String) throws -> String {
+        var mutatedHtml = renderedHtml
+        for mutation in pageMutations {
+            mutatedHtml = try mutation(context, page, mutatedHtml)
+        }
+        mutatedHtml = try mutateHtml(context: context, location: page, renderedHtml: mutatedHtml)
+        return mutatedHtml
+    }
+
+    func mutateHtml(context: PublishingContext<Site>, location: Location, renderedHtml: String) throws -> String {
+        var mutatedHtml = renderedHtml
+        for mutation in allMutations {
+            mutatedHtml = try mutation(context, location, mutatedHtml)
+        }
+        return mutatedHtml
+    }
+
+}
+