diff --git a/tracing-subscriber/src/fmt/fmt_layer.rs b/tracing-subscriber/src/fmt/fmt_layer.rs
index d3cb8c1ed5..c2efaa73d8 100644
--- a/tracing-subscriber/src/fmt/fmt_layer.rs
+++ b/tracing-subscriber/src/fmt/fmt_layer.rs
@@ -71,6 +71,7 @@ pub struct Layer<
     fmt_fields: N,
     fmt_event: E,
     fmt_span: format::FmtSpanConfig,
+    needs_span_fields: bool,
     is_ansi: bool,
     log_internal_errors: bool,
     _inner: PhantomData<fn(S)>,
@@ -120,6 +121,7 @@ where
             fmt_fields: self.fmt_fields,
             fmt_event: e,
             fmt_span: self.fmt_span,
+            needs_span_fields: self.needs_span_fields,
             make_writer: self.make_writer,
             is_ansi: self.is_ansi,
             log_internal_errors: self.log_internal_errors,
@@ -150,6 +152,7 @@ where
             fmt_fields: self.fmt_fields,
             fmt_event: f(self.fmt_event),
             fmt_span: self.fmt_span,
+            needs_span_fields: self.needs_span_fields,
             make_writer: self.make_writer,
             is_ansi: self.is_ansi,
             log_internal_errors: self.log_internal_errors,
@@ -184,6 +187,7 @@ impl<S, N, E, W> Layer<S, N, E, W> {
             fmt_fields: self.fmt_fields,
             fmt_event: self.fmt_event,
             fmt_span: self.fmt_span,
+            needs_span_fields: self.needs_span_fields,
             is_ansi: self.is_ansi,
             log_internal_errors: self.log_internal_errors,
             make_writer,
@@ -268,6 +272,7 @@ impl<S, N, E, W> Layer<S, N, E, W> {
             fmt_fields: self.fmt_fields,
             fmt_event: self.fmt_event,
             fmt_span: self.fmt_span,
+            needs_span_fields: self.needs_span_fields,
             is_ansi: self.is_ansi,
             log_internal_errors: self.log_internal_errors,
             make_writer: TestWriter::default(),
@@ -364,6 +369,7 @@ impl<S, N, E, W> Layer<S, N, E, W> {
             fmt_fields: self.fmt_fields,
             fmt_event: self.fmt_event,
             fmt_span: self.fmt_span,
+            needs_span_fields: self.needs_span_fields,
             is_ansi: self.is_ansi,
             log_internal_errors: self.log_internal_errors,
             make_writer: f(self.make_writer),
@@ -395,6 +401,7 @@ where
             fmt_event: self.fmt_event.with_timer(timer),
             fmt_fields: self.fmt_fields,
             fmt_span: self.fmt_span,
+            needs_span_fields: self.needs_span_fields,
             make_writer: self.make_writer,
             is_ansi: self.is_ansi,
             log_internal_errors: self.log_internal_errors,
@@ -408,6 +415,7 @@ where
             fmt_event: self.fmt_event.without_time(),
             fmt_fields: self.fmt_fields,
             fmt_span: self.fmt_span.without_time(),
+            needs_span_fields: self.needs_span_fields,
             make_writer: self.make_writer,
             is_ansi: self.is_ansi,
             log_internal_errors: self.log_internal_errors,
@@ -537,6 +545,7 @@ where
             fmt_event: self.fmt_event.compact(),
             fmt_fields: self.fmt_fields,
             fmt_span: self.fmt_span,
+            needs_span_fields: self.needs_span_fields,
             make_writer: self.make_writer,
             is_ansi: self.is_ansi,
             log_internal_errors: self.log_internal_errors,
@@ -552,6 +561,7 @@ where
             fmt_event: self.fmt_event.pretty(),
             fmt_fields: format::Pretty::default(),
             fmt_span: self.fmt_span,
+            needs_span_fields: self.needs_span_fields,
             make_writer: self.make_writer,
             is_ansi: self.is_ansi,
             log_internal_errors: self.log_internal_errors,
@@ -582,6 +592,7 @@ where
             fmt_event: self.fmt_event.json(),
             fmt_fields: format::JsonFields::new(),
             fmt_span: self.fmt_span,
+            needs_span_fields: self.needs_span_fields,
             make_writer: self.make_writer,
             // always disable ANSI escapes in JSON mode!
             is_ansi: false,
@@ -601,8 +612,9 @@ impl<S, T, W> Layer<S, format::JsonFields, format::Format<format::Json, T>, W> {
         self,
         flatten_event: bool,
     ) -> Layer<S, format::JsonFields, format::Format<format::Json, T>, W> {
+        let fmt_event = self.fmt_event.flatten_event(flatten_event);
         Layer {
-            fmt_event: self.fmt_event.flatten_event(flatten_event),
+            fmt_event,
             fmt_fields: format::JsonFields::new(),
             ..self
         }
@@ -616,9 +628,13 @@ impl<S, T, W> Layer<S, format::JsonFields, format::Format<format::Json, T>, W> {
         self,
         display_current_span: bool,
     ) -> Layer<S, format::JsonFields, format::Format<format::Json, T>, W> {
+        let fmt_event = self.fmt_event.with_current_span(display_current_span);
+        let needs_span_fields =
+            fmt_event.format.display_current_span || fmt_event.format.display_span_list;
         Layer {
-            fmt_event: self.fmt_event.with_current_span(display_current_span),
+            fmt_event,
             fmt_fields: format::JsonFields::new(),
+            needs_span_fields,
             ..self
         }
     }
@@ -631,9 +647,13 @@ impl<S, T, W> Layer<S, format::JsonFields, format::Format<format::Json, T>, W> {
         self,
         display_span_list: bool,
     ) -> Layer<S, format::JsonFields, format::Format<format::Json, T>, W> {
+        let fmt_event = self.fmt_event.with_span_list(display_span_list);
+        let needs_span_fields =
+            fmt_event.format.display_current_span || fmt_event.format.display_span_list;
         Layer {
-            fmt_event: self.fmt_event.with_span_list(display_span_list),
+            fmt_event,
             fmt_fields: format::JsonFields::new(),
+            needs_span_fields,
             ..self
         }
     }
@@ -650,6 +670,7 @@ impl<S, N, E, W> Layer<S, N, E, W> {
             fmt_event: self.fmt_event,
             fmt_fields,
             fmt_span: self.fmt_span,
+            needs_span_fields: self.needs_span_fields,
             make_writer: self.make_writer,
             is_ansi: self.is_ansi,
             log_internal_errors: self.log_internal_errors,
@@ -681,6 +702,7 @@ impl<S, N, E, W> Layer<S, N, E, W> {
             fmt_event: self.fmt_event,
             fmt_fields: f(self.fmt_fields),
             fmt_span: self.fmt_span,
+            needs_span_fields: self.needs_span_fields,
             make_writer: self.make_writer,
             is_ansi: self.is_ansi,
             log_internal_errors: self.log_internal_errors,
@@ -699,6 +721,7 @@ impl<S> Default for Layer<S> {
             fmt_fields: format::DefaultFields::default(),
             fmt_event: format::Format::default(),
             fmt_span: format::FmtSpanConfig::default(),
+            needs_span_fields: true,
             make_writer: io::stdout,
             is_ansi: ansi,
             log_internal_errors: false,
@@ -812,7 +835,7 @@ where
         let span = ctx.span(id).expect("Span not found, this is a bug");
         let mut extensions = span.extensions_mut();
 
-        if extensions.get_mut::<FormattedFields<N>>().is_none() {
+        if self.needs_span_fields && extensions.get_mut::<FormattedFields<N>>().is_none() {
             let mut fields = FormattedFields::<N>::new(String::new());
             if self
                 .fmt_fields
@@ -846,6 +869,10 @@ where
     }
 
     fn on_record(&self, id: &Id, values: &Record<'_>, ctx: Context<'_, S>) {
+        if !self.needs_span_fields {
+            return;
+        }
+
         let span = ctx.span(id).expect("Span not found, this is a bug");
         let mut extensions = span.extensions_mut();
         if let Some(fields) = extensions.get_mut::<FormattedFields<N>>() {
diff --git a/tracing-subscriber/src/fmt/format/mod.rs b/tracing-subscriber/src/fmt/format/mod.rs
index 80612e1ec2..6573d51581 100644
--- a/tracing-subscriber/src/fmt/format/mod.rs
+++ b/tracing-subscriber/src/fmt/format/mod.rs
@@ -399,7 +399,7 @@ pub struct Full;
 /// intended for use in development.
 #[derive(Debug, Clone)]
 pub struct Format<F = Full, T = SystemTime> {
-    format: F,
+    pub(crate) format: F,
     pub(crate) timer: T,
     pub(crate) ansi: Option<bool>,
     pub(crate) display_timestamp: bool,
@@ -2117,6 +2117,47 @@ pub(super) mod test {
         }
     }
 
+    mod json {
+        use core::cell::Cell;
+
+        use super::*;
+
+        struct CountDebugCalls(Cell<usize>);
+
+        impl fmt::Debug for CountDebugCalls {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                let value = self.0.get() + 1;
+                self.0.set(value);
+                write!(f, "CountDebugCalls({value})")
+            }
+        }
+
+        #[test]
+        fn does_not_record_span_fields() {
+            let make_writer = MockMakeWriter::default();
+            let subscriber = crate::fmt::Subscriber::builder()
+                .json()
+                .with_current_span(false)
+                .with_span_list(false)
+                .with_writer(make_writer.clone())
+                .with_timer(MockTime);
+            let _default = set_default(&subscriber.into());
+
+            let count_debug_calls = CountDebugCalls(Cell::default());
+
+            let span = tracing::info_span!("a span", fields = ?count_debug_calls);
+            let _guard = span.enter();
+            tracing::info!("an event");
+
+            let result = make_writer.get_string();
+            assert_eq!(
+                result.trim(),
+                r#"{"timestamp":"fake time","level":"INFO","fields":{"message":"an event"},"target":"tracing_subscriber::fmt::format::test::json"}"#
+            );
+            assert_eq!(count_debug_calls.0.get(), 0);
+        }
+    }
+
     #[test]
     fn format_nanos() {
         fn fmt(t: u64) -> String {