diff --git a/quickwit/quickwit-config/src/index_config/mod.rs b/quickwit/quickwit-config/src/index_config/mod.rs
index c15d9f3c9db..e0807820009 100644
--- a/quickwit/quickwit-config/src/index_config/mod.rs
+++ b/quickwit/quickwit-config/src/index_config/mod.rs
@@ -90,6 +90,9 @@ pub struct DocMapping {
     pub max_num_partitions: NonZeroU32,
     #[serde(default)]
     pub tokenizers: Vec<TokenizerEntry>,
+    /// Record document length
+    #[serde(default)]
+    pub document_length: bool,
 }
 
 #[derive(Clone, Debug, Serialize, Deserialize, utoipa::ToSchema)]
@@ -454,6 +457,7 @@ impl TestableForRegression for IndexConfig {
             max_num_partitions: NonZeroU32::new(100).unwrap(),
             timestamp_field: Some("timestamp".to_string()),
             tokenizers: vec![tokenizer],
+            document_length: false,
         };
         let retention_policy = Some(RetentionPolicy {
             retention_period: "90 days".to_string(),
@@ -531,6 +535,7 @@ pub fn build_doc_mapper(
         partition_key: doc_mapping.partition_key.clone(),
         max_num_partitions: doc_mapping.max_num_partitions,
         tokenizers: doc_mapping.tokenizers.clone(),
+        document_length: doc_mapping.document_length,
     };
     Ok(Arc::new(builder.try_build()?))
 }
diff --git a/quickwit/quickwit-doc-mapper/src/default_doc_mapper/default_mapper.rs b/quickwit/quickwit-doc-mapper/src/default_doc_mapper/default_mapper.rs
index 10a62caf567..1f4ec83b63d 100644
--- a/quickwit/quickwit-doc-mapper/src/default_doc_mapper/default_mapper.rs
+++ b/quickwit/quickwit-doc-mapper/src/default_doc_mapper/default_mapper.rs
@@ -46,7 +46,7 @@ use crate::query_builder::build_query;
 use crate::routing_expression::RoutingExpr;
 use crate::{
     Cardinality, DocMapper, DocParsingError, Mode, QueryParserError, TokenizerEntry, WarmupInfo,
-    DYNAMIC_FIELD_NAME, FIELD_PRESENCE_FIELD_NAME, SOURCE_FIELD_NAME,
+    DOCUMENT_LEN_FIELD_NAME, DYNAMIC_FIELD_NAME, FIELD_PRESENCE_FIELD_NAME, SOURCE_FIELD_NAME,
 };
 
 const FIELD_PRESENCE_FIELD: Field = Field::from_field_id(0u32);
@@ -69,6 +69,8 @@ pub struct DefaultDocMapper {
     /// This field is only valid when using the schema associated with the default
     /// doc mapper, and therefore cannot be used in the `query` method.
     dynamic_field: Option<Field>,
+    /// Field in which the len of the source document is stored as a fast field.
+    document_len_field: Option<Field>,
     /// Default list of field names used for search.
     default_search_field_names: Vec<String>,
     /// Timestamp field name.
@@ -158,6 +160,13 @@ impl TryFrom<DefaultDocMapperBuilder> for DefaultDocMapper {
             None
         };
 
+        let document_len_field = if builder.document_length {
+            let document_len_field_options = tantivy::schema::NumericOptions::default().set_fast();
+            Some(schema_builder.add_u64_field(DOCUMENT_LEN_FIELD_NAME, document_len_field_options))
+        } else {
+            None
+        };
+
         // Adding regular fields.
         let MappingNodeRoot {
             field_mappings,
@@ -226,7 +235,6 @@ impl TryFrom<DefaultDocMapperBuilder> for DefaultDocMapper {
                     default_search_field_name
                 )
             }
-            let dynamic_field = schema.get_field(DYNAMIC_FIELD_NAME).ok();
             let (default_search_field, _json_path) = schema
                 .find_field_with_default(default_search_field_name, dynamic_field)
                 .with_context(|| {
@@ -262,6 +270,7 @@ impl TryFrom<DefaultDocMapperBuilder> for DefaultDocMapper {
             index_field_presence: builder.index_field_presence,
             source_field,
             dynamic_field,
+            document_len_field,
             default_search_field_names,
             timestamp_field_name: builder.timestamp_field,
             field_mappings,
@@ -378,6 +387,7 @@ impl From<DefaultDocMapper> for DefaultDocMapperBuilder {
             partition_key: partition_key_opt,
             max_num_partitions: default_doc_mapper.max_num_partitions,
             tokenizers: default_doc_mapper.tokenizer_entries,
+            document_length: false,
         }
     }
 }
@@ -561,6 +571,7 @@ impl DocMapper for DefaultDocMapper {
     fn doc_from_json_obj(
         &self,
         json_obj: JsonObject,
+        document_len: u64,
     ) -> Result<(Partition, Document), DocParsingError> {
         let partition: Partition = self.partition_key.eval_hash(&json_obj);
 
@@ -613,6 +624,10 @@ impl DocMapper for DefaultDocMapper {
             }
         }
 
+        if let Some(document_len_field) = self.document_len_field {
+            document.add_u64(document_len_field, document_len);
+        }
+
         // The capacity is inexact here.
 
         if self.index_field_presence {
@@ -729,8 +744,8 @@ mod tests {
     use crate::default_doc_mapper::field_mapping_entry::DEFAULT_TOKENIZER_NAME;
     use crate::default_doc_mapper::mapping_tree::value_to_pretokenized;
     use crate::{
-        DefaultDocMapperBuilder, DocMapper, DocParsingError, DYNAMIC_FIELD_NAME,
-        FIELD_PRESENCE_FIELD_NAME, SOURCE_FIELD_NAME,
+        DefaultDocMapperBuilder, DocMapper, DocParsingError, DOCUMENT_LEN_FIELD_NAME,
+        DYNAMIC_FIELD_NAME, FIELD_PRESENCE_FIELD_NAME, SOURCE_FIELD_NAME,
     };
 
     fn example_json_doc_value() -> JsonValue {
@@ -786,7 +801,7 @@ mod tests {
         let json_doc = example_json_doc_value();
         let doc_mapper = crate::default_doc_mapper_for_test();
         let (_, document) = doc_mapper
-            .doc_from_json_obj(json_doc.as_object().unwrap().clone())
+            .doc_from_json_obj(json_doc.as_object().unwrap().clone(), 0)
             .unwrap();
         let schema = doc_mapper.schema();
         // 9 property entry + 1 field "_source" + 2 fields values for "tags" field
@@ -1265,7 +1280,7 @@ mod tests {
             "image": "YWJj"
         });
         let (_, document) = doc_mapper
-            .doc_from_json_obj(json_doc_value.as_object().unwrap().clone())
+            .doc_from_json_obj(json_doc_value.as_object().unwrap().clone(), 0)
             .unwrap();
 
         // 2 properties, + 1 value for "_source" + 2 for field presence.
@@ -2014,6 +2029,20 @@ mod tests {
         );
     }
 
+    #[test]
+    fn test_length_field() {
+        let raw_doc = r#"{ "some_obj": { "json_obj": {"hello": 2} } }"#;
+        test_doc_from_json_test_aux(
+            r#"{
+                "document_length": true,
+                "mode": "dynamic"
+            }"#,
+            DOCUMENT_LEN_FIELD_NAME,
+            raw_doc,
+            vec![(raw_doc.len() as u64).into()],
+        );
+    }
+
     fn default_doc_mapper_query_aux(
         doc_mapper: &dyn DocMapper,
         query: &str,
diff --git a/quickwit/quickwit-doc-mapper/src/default_doc_mapper/default_mapper_builder.rs b/quickwit/quickwit-doc-mapper/src/default_doc_mapper/default_mapper_builder.rs
index 4aeb756cc6a..2c60d137384 100644
--- a/quickwit/quickwit-doc-mapper/src/default_doc_mapper/default_mapper_builder.rs
+++ b/quickwit/quickwit-doc-mapper/src/default_doc_mapper/default_mapper_builder.rs
@@ -80,6 +80,9 @@ pub struct DefaultDocMapperBuilder {
     /// User-defined tokenizers.
     #[serde(default)]
     pub tokenizers: Vec<TokenizerEntry>,
+    /// Record document length
+    #[serde(default)]
+    pub document_length: bool,
 }
 
 /// Defines how an unmapped field should be handled.
diff --git a/quickwit/quickwit-doc-mapper/src/doc_mapper.rs b/quickwit/quickwit-doc-mapper/src/doc_mapper.rs
index f8330e2ac4b..04860c47c97 100644
--- a/quickwit/quickwit-doc-mapper/src/doc_mapper.rs
+++ b/quickwit/quickwit-doc-mapper/src/doc_mapper.rs
@@ -52,6 +52,7 @@ pub trait DocMapper: Send + Sync + Debug + DynClone + 'static {
     fn doc_from_json_obj(
         &self,
         json_obj: JsonObject,
+        document_len: u64,
     ) -> Result<(Partition, Document), DocParsingError>;
 
     /// Parses a JSON byte slice into a tantivy [`Document`].
@@ -65,7 +66,7 @@ pub trait DocMapper: Send + Sync + Debug + DynClone + 'static {
                 .unwrap_or_else(|_| "document contains some invalid UTF-8 characters".to_string());
             DocParsingError::NotJsonObject(json_doc_sample)
         })?;
-        self.doc_from_json_obj(json_obj)
+        self.doc_from_json_obj(json_obj, json_doc.len() as u64)
     }
 
     /// Parses a JSON string into a tantivy [`Document`].
@@ -74,7 +75,7 @@ pub trait DocMapper: Send + Sync + Debug + DynClone + 'static {
             let json_doc_sample: String = json_doc.chars().take(20).chain("...".chars()).collect();
             DocParsingError::NotJsonObject(json_doc_sample)
         })?;
-        self.doc_from_json_obj(json_obj)
+        self.doc_from_json_obj(json_obj, json_doc.len() as u64)
     }
 
     /// Converts a tantivy named Document to the json format.
diff --git a/quickwit/quickwit-doc-mapper/src/lib.rs b/quickwit/quickwit-doc-mapper/src/lib.rs
index 0912f49a20e..161732b28f5 100644
--- a/quickwit/quickwit-doc-mapper/src/lib.rs
+++ b/quickwit/quickwit-doc-mapper/src/lib.rs
@@ -55,11 +55,15 @@ pub const SOURCE_FIELD_NAME: &str = "_source";
 /// Field name reserved for storing the dynamically indexed fields.
 pub const DYNAMIC_FIELD_NAME: &str = "_dynamic";
 
+/// Field name reserved for storing the length of source document.
+pub const DOCUMENT_LEN_FIELD_NAME: &str = "_doc_length";
+
 /// Quickwit reserved field names.
 const QW_RESERVED_FIELD_NAMES: &[&str] = &[
     SOURCE_FIELD_NAME,
     DYNAMIC_FIELD_NAME,
     FIELD_PRESENCE_FIELD_NAME,
+    DOCUMENT_LEN_FIELD_NAME,
 ];
 
 /// Cardinality of a field.
diff --git a/quickwit/quickwit-indexing/src/actors/doc_processor.rs b/quickwit/quickwit-indexing/src/actors/doc_processor.rs
index 6423c8e8c9a..b3c7f84ee21 100644
--- a/quickwit/quickwit-indexing/src/actors/doc_processor.rs
+++ b/quickwit/quickwit-indexing/src/actors/doc_processor.rs
@@ -461,7 +461,9 @@ impl DocProcessor {
     fn process_json_doc(&self, json_doc: JsonDoc) -> Result<ProcessedDoc, DocProcessorError> {
         let num_bytes = json_doc.num_bytes;
 
-        let (partition, doc) = self.doc_mapper.doc_from_json_obj(json_doc.json_obj)?;
+        let (partition, doc) = self
+            .doc_mapper
+            .doc_from_json_obj(json_doc.json_obj, json_doc.num_bytes as u64)?;
         let timestamp_opt = self.extract_timestamp(&doc)?;
         Ok(ProcessedDoc {
             doc,
diff --git a/quickwit/quickwit-metastore/test-data/file-backed-index/v0.6.expected.json b/quickwit/quickwit-metastore/test-data/file-backed-index/v0.6.expected.json
index 30dff33588b..f8f5b4e6f01 100644
--- a/quickwit/quickwit-metastore/test-data/file-backed-index/v0.6.expected.json
+++ b/quickwit/quickwit-metastore/test-data/file-backed-index/v0.6.expected.json
@@ -18,6 +18,7 @@
     "create_timestamp": 1789,
     "index_config": {
       "doc_mapping": {
+        "document_length": false,
         "dynamic_mapping": {
           "expand_dots": true,
           "fast": {
diff --git a/quickwit/quickwit-metastore/test-data/file-backed-index/v0.7.expected.json b/quickwit/quickwit-metastore/test-data/file-backed-index/v0.7.expected.json
index 8af520d4800..643b3b8e4fe 100644
--- a/quickwit/quickwit-metastore/test-data/file-backed-index/v0.7.expected.json
+++ b/quickwit/quickwit-metastore/test-data/file-backed-index/v0.7.expected.json
@@ -18,6 +18,7 @@
     "create_timestamp": 1789,
     "index_config": {
       "doc_mapping": {
+        "document_length": false,
         "dynamic_mapping": {
           "expand_dots": true,
           "fast": {
diff --git a/quickwit/quickwit-metastore/test-data/file-backed-index/v0.8.expected.json b/quickwit/quickwit-metastore/test-data/file-backed-index/v0.8.expected.json
index 8af520d4800..643b3b8e4fe 100644
--- a/quickwit/quickwit-metastore/test-data/file-backed-index/v0.8.expected.json
+++ b/quickwit/quickwit-metastore/test-data/file-backed-index/v0.8.expected.json
@@ -18,6 +18,7 @@
     "create_timestamp": 1789,
     "index_config": {
       "doc_mapping": {
+        "document_length": false,
         "dynamic_mapping": {
           "expand_dots": true,
           "fast": {
diff --git a/quickwit/quickwit-metastore/test-data/file-backed-index/v0.8.json b/quickwit/quickwit-metastore/test-data/file-backed-index/v0.8.json
index 8af520d4800..643b3b8e4fe 100644
--- a/quickwit/quickwit-metastore/test-data/file-backed-index/v0.8.json
+++ b/quickwit/quickwit-metastore/test-data/file-backed-index/v0.8.json
@@ -18,6 +18,7 @@
     "create_timestamp": 1789,
     "index_config": {
       "doc_mapping": {
+        "document_length": false,
         "dynamic_mapping": {
           "expand_dots": true,
           "fast": {
diff --git a/quickwit/quickwit-metastore/test-data/index-metadata/v0.4.expected.json b/quickwit/quickwit-metastore/test-data/index-metadata/v0.4.expected.json
index 9411c58dde3..574dc5d0324 100644
--- a/quickwit/quickwit-metastore/test-data/index-metadata/v0.4.expected.json
+++ b/quickwit/quickwit-metastore/test-data/index-metadata/v0.4.expected.json
@@ -7,6 +7,7 @@
   "create_timestamp": 1789,
   "index_config": {
     "doc_mapping": {
+      "document_length": false,
       "dynamic_mapping": {
         "expand_dots": true,
         "fast": {
diff --git a/quickwit/quickwit-metastore/test-data/index-metadata/v0.5.expected.json b/quickwit/quickwit-metastore/test-data/index-metadata/v0.5.expected.json
index 9411c58dde3..574dc5d0324 100644
--- a/quickwit/quickwit-metastore/test-data/index-metadata/v0.5.expected.json
+++ b/quickwit/quickwit-metastore/test-data/index-metadata/v0.5.expected.json
@@ -7,6 +7,7 @@
   "create_timestamp": 1789,
   "index_config": {
     "doc_mapping": {
+      "document_length": false,
       "dynamic_mapping": {
         "expand_dots": true,
         "fast": {
diff --git a/quickwit/quickwit-metastore/test-data/index-metadata/v0.6.expected.json b/quickwit/quickwit-metastore/test-data/index-metadata/v0.6.expected.json
index bd3c52e5e91..52865f45aa2 100644
--- a/quickwit/quickwit-metastore/test-data/index-metadata/v0.6.expected.json
+++ b/quickwit/quickwit-metastore/test-data/index-metadata/v0.6.expected.json
@@ -7,6 +7,7 @@
   "create_timestamp": 1789,
   "index_config": {
     "doc_mapping": {
+      "document_length": false,
       "dynamic_mapping": {
         "expand_dots": true,
         "fast": {
diff --git a/quickwit/quickwit-metastore/test-data/index-metadata/v0.7.expected.json b/quickwit/quickwit-metastore/test-data/index-metadata/v0.7.expected.json
index bd3c52e5e91..52865f45aa2 100644
--- a/quickwit/quickwit-metastore/test-data/index-metadata/v0.7.expected.json
+++ b/quickwit/quickwit-metastore/test-data/index-metadata/v0.7.expected.json
@@ -7,6 +7,7 @@
   "create_timestamp": 1789,
   "index_config": {
     "doc_mapping": {
+      "document_length": false,
       "dynamic_mapping": {
         "expand_dots": true,
         "fast": {
diff --git a/quickwit/quickwit-metastore/test-data/index-metadata/v0.8.expected.json b/quickwit/quickwit-metastore/test-data/index-metadata/v0.8.expected.json
index bd3c52e5e91..52865f45aa2 100644
--- a/quickwit/quickwit-metastore/test-data/index-metadata/v0.8.expected.json
+++ b/quickwit/quickwit-metastore/test-data/index-metadata/v0.8.expected.json
@@ -7,6 +7,7 @@
   "create_timestamp": 1789,
   "index_config": {
     "doc_mapping": {
+      "document_length": false,
       "dynamic_mapping": {
         "expand_dots": true,
         "fast": {
diff --git a/quickwit/quickwit-metastore/test-data/index-metadata/v0.8.json b/quickwit/quickwit-metastore/test-data/index-metadata/v0.8.json
index bd3c52e5e91..52865f45aa2 100644
--- a/quickwit/quickwit-metastore/test-data/index-metadata/v0.8.json
+++ b/quickwit/quickwit-metastore/test-data/index-metadata/v0.8.json
@@ -7,6 +7,7 @@
   "create_timestamp": 1789,
   "index_config": {
     "doc_mapping": {
+      "document_length": false,
       "dynamic_mapping": {
         "expand_dots": true,
         "fast": {
diff --git a/quickwit/quickwit-metastore/test-data/manifest/v0.7.expected.json b/quickwit/quickwit-metastore/test-data/manifest/v0.7.expected.json
index 2f1a2f647ac..d47e828440d 100644
--- a/quickwit/quickwit-metastore/test-data/manifest/v0.7.expected.json
+++ b/quickwit/quickwit-metastore/test-data/manifest/v0.7.expected.json
@@ -8,6 +8,7 @@
     {
       "description": "Test description.",
       "doc_mapping": {
+        "document_length": false,
         "dynamic_mapping": {
           "expand_dots": true,
           "fast": {
diff --git a/quickwit/quickwit-metastore/test-data/manifest/v0.8.expected.json b/quickwit/quickwit-metastore/test-data/manifest/v0.8.expected.json
index 2f1a2f647ac..d47e828440d 100644
--- a/quickwit/quickwit-metastore/test-data/manifest/v0.8.expected.json
+++ b/quickwit/quickwit-metastore/test-data/manifest/v0.8.expected.json
@@ -8,6 +8,7 @@
     {
       "description": "Test description.",
       "doc_mapping": {
+        "document_length": false,
         "dynamic_mapping": {
           "expand_dots": true,
           "fast": {
diff --git a/quickwit/quickwit-metastore/test-data/manifest/v0.8.json b/quickwit/quickwit-metastore/test-data/manifest/v0.8.json
index 2f1a2f647ac..d47e828440d 100644
--- a/quickwit/quickwit-metastore/test-data/manifest/v0.8.json
+++ b/quickwit/quickwit-metastore/test-data/manifest/v0.8.json
@@ -8,6 +8,7 @@
     {
       "description": "Test description.",
       "doc_mapping": {
+        "document_length": false,
         "dynamic_mapping": {
           "expand_dots": true,
           "fast": {
diff --git a/quickwit/quickwit-search/src/collector.rs b/quickwit/quickwit-search/src/collector.rs
index f81722f5282..a59c2b12bfd 100644
--- a/quickwit/quickwit-search/src/collector.rs
+++ b/quickwit/quickwit-search/src/collector.rs
@@ -1488,6 +1488,7 @@ mod tests {
         fn doc_from_json_obj(
             &self,
             _json_obj: quickwit_doc_mapper::JsonObject,
+            _doc_len: u64,
         ) -> Result<(u64, TantivyDocument), quickwit_doc_mapper::DocParsingError> {
             unimplemented!()
         }
diff --git a/quickwit/rest-api-tests/scenarii/aggregations/0002-doc-len.yaml b/quickwit/rest-api-tests/scenarii/aggregations/0002-doc-len.yaml
new file mode 100644
index 00000000000..e98e59a156c
--- /dev/null
+++ b/quickwit/rest-api-tests/scenarii/aggregations/0002-doc-len.yaml
@@ -0,0 +1,32 @@
+# Test summing doc len
+method: [GET]
+engines:
+  - quickwit
+endpoint: _elastic/aggregations/_search
+json:
+  query: { match_all: {} }
+  aggs:
+    doc_len:
+      sum:
+        field: "_doc_length"
+expected:
+  aggregations:
+    doc_len:
+      value: 913.0
+---
+# Test doc len isn't shown when querying documents
+method: [GET]
+engines:
+  - quickwit
+endpoint: _elastic/aggregations/_search
+json:
+  query:
+    term:
+      id:
+        value: 1
+expected:
+  hits:
+    hits:
+      - _source:
+          $expect: "not '_doc_length' in val"
+---
diff --git a/quickwit/rest-api-tests/scenarii/aggregations/_setup.quickwit.yaml b/quickwit/rest-api-tests/scenarii/aggregations/_setup.quickwit.yaml
index 05962fe8828..28cd5a2f6d2 100644
--- a/quickwit/rest-api-tests/scenarii/aggregations/_setup.quickwit.yaml
+++ b/quickwit/rest-api-tests/scenarii/aggregations/_setup.quickwit.yaml
@@ -18,6 +18,7 @@ json:
     dynamic_mapping:
       tokenizer: default
       fast: true
+    document_length: true
     field_mappings:
       - name: date
         type: datetime