diff --git a/codespan-reporting/CHANGELOG.md b/codespan-reporting/CHANGELOG.md
index 14c47660..63ba2a91 100644
--- a/codespan-reporting/CHANGELOG.md
+++ b/codespan-reporting/CHANGELOG.md
@@ -64,6 +64,8 @@ This is because some testing dependencies now require this Rust version.
     ```
 
     </details>
+-   `Label`s can now be created without specifying a file id and instead later setting
+    the file id on a `Label` or all labels in a `Diagnostic`.
 
 ## [0.11.1] - 2021-01-18
 
diff --git a/codespan-reporting/examples/term.rs b/codespan-reporting/examples/term.rs
index ee2c057d..9715f37c 100644
--- a/codespan-reporting/examples/term.rs
+++ b/codespan-reporting/examples/term.rs
@@ -128,12 +128,12 @@ fn main() -> anyhow::Result<()> {
             .with_message("`case` clauses have incompatible types")
             .with_code("E0308")
             .with_labels(vec![
-                Label::primary(file_id3, 163..166).with_message("expected `String`, found `Nat`"),
-                Label::secondary(file_id3, 62..166)
+                Label::primary_anon(163..166).with_message("expected `String`, found `Nat`"),
+                Label::secondary_anon(62..166)
                     .with_message("`case` clauses have incompatible types"),
-                Label::secondary(file_id3, 41..47)
-                    .with_message("expected type `String` found here"),
+                Label::secondary_anon(41..47).with_message("expected type `String` found here"),
             ])
+            .with_file(file_id3)
             .with_notes(vec![unindent::unindent(
                 "
                     expected type `String`
@@ -145,18 +145,18 @@ fn main() -> anyhow::Result<()> {
             .with_message("`case` clauses have incompatible types")
             .with_code("E0308")
             .with_labels(vec![
-                Label::primary(file_id3, 328..331).with_message("expected `String`, found `Nat`"),
-                Label::secondary(file_id3, 211..331)
+                Label::primary_anon(328..331).with_message("expected `String`, found `Nat`"),
+                Label::secondary_anon(211..331)
                     .with_message("`case` clauses have incompatible types"),
-                Label::secondary(file_id3, 258..268)
+                Label::secondary_anon(258..268)
                     .with_message("this is found to be of type `String`"),
-                Label::secondary(file_id3, 284..290)
+                Label::secondary_anon(284..290)
                     .with_message("this is found to be of type `String`"),
-                Label::secondary(file_id3, 306..312)
+                Label::secondary_anon(306..312)
                     .with_message("this is found to be of type `String`"),
-                Label::secondary(file_id3, 186..192)
-                    .with_message("expected type `String` found here"),
+                Label::secondary_anon(186..192).with_message("expected type `String` found here"),
             ])
+            .with_file(file_id3)
             .with_notes(vec![unindent::unindent(
                 "
                     expected type `String`
diff --git a/codespan-reporting/src/diagnostic.rs b/codespan-reporting/src/diagnostic.rs
index 8e3abf4f..871039cf 100644
--- a/codespan-reporting/src/diagnostic.rs
+++ b/codespan-reporting/src/diagnostic.rs
@@ -85,11 +85,58 @@ impl<FileId> Label<FileId> {
         Label::new(LabelStyle::Secondary, file_id, range)
     }
 
-    /// Add a message to the diagnostic.
+    /// Set the message for the diagnostic. The old message (if any) is discarded.
     pub fn with_message(mut self, message: impl ToString) -> Label<FileId> {
         self.message = message.to_string();
         self
     }
+
+    /// Set the file id. The old file id (if any) is discarded.
+    pub fn with_file<NewFileId>(self, file_id: NewFileId) -> Label<NewFileId> {
+        Label {
+            style: self.style,
+            file_id,
+            range: self.range,
+            message: self.message,
+        }
+    }
+}
+
+// use a separate impl so we do not have to specify the type like this in e.g.
+// `primary_anon`:
+// ```
+// Label::<()>::new_anon(..)
+// ```
+impl Label<()> {
+    /// Create a new label without specifying a [`file_id`].
+    ///
+    /// [`file_id`]: Label::file_id
+    pub fn new_anon(style: LabelStyle, range: impl Into<Range<usize>>) -> Label<()> {
+        Label {
+            style,
+            file_id: (),
+            range: range.into(),
+            message: String::new(),
+        }
+    }
+
+    /// Create a new label with a style of [`LabelStyle::Primary`] and without
+    /// specifying a [`file_id`].
+    ///
+    /// [`LabelStyle::Primary`]: LabelStyle::Primary
+    /// [`file_id`]: Label::file_id
+    pub fn primary_anon(range: impl Into<Range<usize>>) -> Label<()> {
+        Label::new_anon(LabelStyle::Primary, range)
+    }
+
+    /// Create a new label with a style of [`LabelStyle::Secondary`] and without
+    /// specifying a [`file_id`].
+    ///
+    /// [`LabelStyle::Secondary`]: LabelStyle::Secondary
+    /// [`file_id`]: Label::file_id
+    pub fn secondary_anon(range: impl Into<Range<usize>>) -> Label<()> {
+        Label::new_anon(LabelStyle::Secondary, range)
+    }
 }
 
 /// Represents a diagnostic message that can provide information like errors and
@@ -188,4 +235,20 @@ impl<FileId> Diagnostic<FileId> {
         self.notes.append(&mut notes);
         self
     }
+
+    /// Set the file id for all labels in this Diagnostic by calling
+    /// [`Label::with_file`] on each label.
+    pub fn with_file<NewFileId: Clone>(mut self, file_id: NewFileId) -> Diagnostic<NewFileId> {
+        Diagnostic {
+            severity: self.severity,
+            code: self.code,
+            message: self.message,
+            labels: self
+                .labels
+                .drain(..)
+                .map(|label| label.with_file(file_id.clone()))
+                .collect(),
+            notes: self.notes,
+        }
+    }
 }