diff --git a/milli/Cargo.toml b/milli/Cargo.toml
index 37c7b7c84..318a2604a 100644
--- a/milli/Cargo.toml
+++ b/milli/Cargo.toml
@@ -51,8 +51,11 @@ csv = "1.1.6"
 
 [dev-dependencies]
 big_s = "1.0.2"
+insta = "1.17.1"
 maplit = "1.0.2"
+md5 = "0.7.0"
 rand = "0.8.5"
+regex = "1.6.0"
 
 [features]
 default = []
diff --git a/milli/src/lib.rs b/milli/src/lib.rs
index 09cecb228..85b25cad1 100644
--- a/milli/src/lib.rs
+++ b/milli/src/lib.rs
@@ -13,6 +13,10 @@ pub mod proximity;
 mod search;
 pub mod update;
 
+#[cfg(test)]
+#[macro_use]
+pub mod snapshot_tests;
+
 use std::collections::{BTreeMap, HashMap};
 use std::convert::{TryFrom, TryInto};
 use std::hash::BuildHasherDefault;
diff --git a/milli/src/snapshot_tests.rs b/milli/src/snapshot_tests.rs
new file mode 100644
index 000000000..aa1d5cf27
--- /dev/null
+++ b/milli/src/snapshot_tests.rs
@@ -0,0 +1,320 @@
+use heed::BytesDecode;
+use roaring::RoaringBitmap;
+use std::path::Path;
+
+use crate::{
+    heed_codec::facet::{
+        FacetLevelValueU32Codec, FacetStringLevelZeroCodec, FacetStringLevelZeroValueCodec,
+        FacetStringZeroBoundsValueCodec,
+    },
+    CboRoaringBitmapCodec, ExternalDocumentsIds, Index,
+};
+
+macro_rules! snapshot_index {
+    ($index:expr, $name:expr) => {
+        $crate::index::tests::snapshot_index($index, $name, None, None)
+    };
+    ($index:expr, $name:expr, include: $regex:literal) => {
+        $crate::index::tests::snapshot_index(
+            $index,
+            $name,
+            Some(regex::Regex::new($regex).unwrap()),
+            None,
+        )
+    };
+    ($index:expr, $name:expr, exclude: $regex:literal) => {
+        $crate::index::tests::snapshot_index(
+            $index,
+            $name,
+            None,
+            Some(regex::Regex::new($regex).unwrap()),
+        )
+    };
+}
+
+#[track_caller]
+pub fn snapshot_index(
+    index: &Index,
+    name: &str,
+    include: Option<regex::Regex>,
+    exclude: Option<regex::Regex>,
+) {
+    use std::fmt::Write;
+
+    let should_snapshot = |name: &str| -> bool {
+        include.as_ref().map(|f| f.is_match(name)).unwrap_or(true)
+            && !exclude.as_ref().map(|f| f.is_match(name)).unwrap_or(false)
+    };
+
+    let mut settings = insta::Settings::clone_current();
+    settings.set_prepend_module_to_snapshot(false);
+    let path = Path::new(std::panic::Location::caller().file());
+    let path = path.strip_prefix("milli/src").unwrap();
+    settings.set_omit_expression(true);
+    settings.set_snapshot_path(Path::new("snapshots").join(path).join(name));
+    let rtxn = index.read_txn().unwrap();
+
+    let store_whole_snapshot = std::env::var("MILLI_TEST_FULL_SNAPS").unwrap_or("false".to_owned());
+    let store_whole_snapshot: bool = store_whole_snapshot.parse().unwrap();
+
+    macro_rules! snapshot_db {
+        ($name:ident, |$vars:pat| $push:block) => {
+            let name_str = stringify!($name);
+            if should_snapshot(name_str) {
+                let iter = index.$name.iter(&rtxn).unwrap();
+                let mut snap = String::new();
+                for x in iter {
+                    let $vars = x.unwrap();
+                    snap.push_str($push);
+                    snap.push('\n');
+                }
+                if snap.len() < 512 {
+                    insta::assert_snapshot!(name_str, snap);
+                } else {
+                    if store_whole_snapshot {
+                        insta::assert_snapshot!(format!("{name_str}.full"), snap);
+                    }
+                    let hash = md5::compute(snap.as_bytes());
+                    let hash_str = format!("{hash:x}");
+                    insta::assert_snapshot!(format!("{name_str}.hash"), hash_str);
+                }
+            }
+        };
+    }
+
+    fn display_bitmap(b: &RoaringBitmap) -> String {
+        let mut s = String::new();
+        s.push('[');
+        for x in b.into_iter() {
+            write!(&mut s, "{x}, ").unwrap();
+        }
+        s.push(']');
+        s
+    }
+
+    settings.bind(|| {
+        snapshot_db!(word_docids, |(s, b)| { &format!("{s:<16} {}", display_bitmap(&b)) });
+        snapshot_db!(exact_word_docids, |(s, b)| { &format!("{s:<16} {}", display_bitmap(&b)) });
+        snapshot_db!(word_prefix_docids, |(s, b)| { &format!("{s:<16} {}", display_bitmap(&b)) });
+        snapshot_db!(exact_word_prefix_docids, |(s, b)| {
+            &format!("{s:<16} {}", display_bitmap(&b))
+        });
+
+        snapshot_db!(docid_word_positions, |((idx, s), b)| {
+            &format!("{idx:<6} {s:<16} {}", display_bitmap(&b))
+        });
+
+        snapshot_db!(word_pair_proximity_docids, |((word1, word2, proximity), b)| {
+            &format!("{word1:<16} {word2:<16} {proximity:<2} {}", display_bitmap(&b))
+        });
+
+        snapshot_db!(word_prefix_pair_proximity_docids, |((word1, prefix, proximity), b)| {
+            &format!("{word1:<16} {prefix:<4} {proximity:<2} {}", display_bitmap(&b))
+        });
+
+        snapshot_db!(word_position_docids, |((word, position), b)| {
+            &format!("{word:<16} {position:<6} {}", display_bitmap(&b))
+        });
+
+        snapshot_db!(field_id_word_count_docids, |((field_id, word_count), b)| {
+            &format!("{field_id:<3} {word_count:<6} {}", display_bitmap(&b))
+        });
+
+        snapshot_db!(word_prefix_position_docids, |((word_prefix, position), b)| {
+            &format!("{word_prefix:<4} {position:<6} {}", display_bitmap(&b))
+        });
+
+        snapshot_db!(facet_id_f64_docids, |((facet_id, level, left, right), b)| {
+            &format!("{facet_id:<3} {level:<2} {left:<6} {right:<6} {}", display_bitmap(&b))
+        });
+        {
+            let name_str = stringify!(facet_id_string_docids);
+            if should_snapshot(name_str) {
+                let bytes_db = index.facet_id_string_docids.remap_types::<ByteSlice, ByteSlice>();
+                let iter = bytes_db.iter(&rtxn).unwrap();
+                let mut snap = String::new();
+
+                for x in iter {
+                    let (key, value) = x.unwrap();
+                    if let Some((field_id, normalized_str)) =
+                        FacetStringLevelZeroCodec::bytes_decode(key)
+                    {
+                        let (orig_string, docids) =
+                            FacetStringLevelZeroValueCodec::bytes_decode(value).unwrap();
+                        snap.push_str(&format!(
+                            "{field_id:<3} {normalized_str:<8} {orig_string:<8} {}\n",
+                            display_bitmap(&docids)
+                        ));
+                    } else if let Some((field_id, level, left, right)) =
+                        FacetLevelValueU32Codec::bytes_decode(key)
+                    {
+                        snap.push_str(&format!("{field_id:<3} {level:<2} {left:<6} {right:<6} "));
+                        let (bounds, docids) = FacetStringZeroBoundsValueCodec::<
+                            CboRoaringBitmapCodec,
+                        >::bytes_decode(value)
+                        .unwrap();
+                        if let Some((left, right)) = bounds {
+                            snap.push_str(&format!("{left:<8} {right:<8} "));
+                        }
+                        snap.push_str(&display_bitmap(&docids));
+                        snap.push('\n');
+                    } else {
+                        panic!();
+                    }
+                }
+                insta::assert_snapshot!(name_str, snap);
+            }
+        }
+
+        // Main - computed settings
+        {
+            let mut snap = String::new();
+
+            macro_rules! write_setting_to_snap {
+                ($name:ident) => {
+                    if should_snapshot(&format!("settings.{}", stringify!($name))) {
+                        let $name = index.$name(&rtxn).unwrap();
+                        writeln!(&mut snap, "{}: {:?}", stringify!($name), $name).unwrap();
+                    }
+                };
+            }
+            write_setting_to_snap!(primary_key);
+            write_setting_to_snap!(criteria);
+            write_setting_to_snap!(displayed_fields);
+            write_setting_to_snap!(distinct_field);
+            write_setting_to_snap!(filterable_fields);
+            write_setting_to_snap!(sortable_fields);
+            write_setting_to_snap!(synonyms);
+            write_setting_to_snap!(authorize_typos);
+            write_setting_to_snap!(min_word_len_one_typo);
+            write_setting_to_snap!(min_word_len_two_typos);
+            write_setting_to_snap!(exact_words);
+            write_setting_to_snap!(exact_attributes);
+            write_setting_to_snap!(max_values_per_facet);
+            write_setting_to_snap!(pagination_max_total_hits);
+            write_setting_to_snap!(searchable_fields);
+            write_setting_to_snap!(user_defined_searchable_fields);
+
+            if !snap.is_empty() {
+                insta::assert_snapshot!("settings", snap);
+            }
+        }
+        // Main - others
+        {
+            macro_rules! snapshot_string {
+                ($name:ident) => {
+                    if should_snapshot(&format!("{}", stringify!($name))) {
+                        insta::assert_snapshot!(stringify!($name), $name);
+                    }
+                };
+            }
+            {
+                let documents_ids = index.documents_ids(&rtxn).unwrap();
+                let documents_ids = display_bitmap(&documents_ids);
+                snapshot_string!(documents_ids);
+            }
+            {
+                let stop_words = index.stop_words(&rtxn).unwrap();
+                let stop_words = format!("{stop_words:?}");
+                snapshot_string!(stop_words);
+            }
+            {
+                let soft_deleted_documents_ids = index.soft_deleted_documents_ids(&rtxn).unwrap();
+                let soft_deleted_documents_ids = display_bitmap(&soft_deleted_documents_ids);
+                snapshot_string!(soft_deleted_documents_ids);
+            }
+
+            {
+                let mut field_distribution = String::new();
+                for (field, count) in index.field_distribution(&rtxn).unwrap() {
+                    writeln!(&mut field_distribution, "{field:<16} {count:<6}").unwrap();
+                }
+                snapshot_string!(field_distribution);
+            }
+            let fields_ids_map = index.fields_ids_map(&rtxn).unwrap();
+            {
+                let mut snap = String::new();
+                for field_id in fields_ids_map.ids() {
+                    let name = fields_ids_map.name(field_id).unwrap();
+                    writeln!(&mut snap, "{field_id:<3} {name:<16}").unwrap();
+                }
+                let fields_ids_map = snap;
+                snapshot_string!(fields_ids_map);
+            }
+
+            {
+                let geo_faceted_documents_ids = index.geo_faceted_documents_ids(&rtxn).unwrap();
+                let geo_faceted_documents_ids = display_bitmap(&geo_faceted_documents_ids);
+                snapshot_string!(geo_faceted_documents_ids);
+            }
+            // let geo_rtree = index.geo_rtree(&rtxn).unwrap();
+            {
+                let ExternalDocumentsIds { soft, hard, .. } =
+                    index.external_documents_ids(&rtxn).unwrap();
+                let mut external_documents_ids = String::new();
+                let soft_bytes = soft.into_fst().as_bytes().to_owned();
+                let mut hex_soft = String::new();
+                for byte in soft_bytes {
+                    write!(&mut hex_soft, "{:x}", byte).unwrap();
+                }
+                writeln!(&mut external_documents_ids, "soft: {hex_soft}").unwrap();
+                let hard_bytes = hard.into_fst().as_bytes().to_owned();
+                let mut hex_hard = String::new();
+                for byte in hard_bytes {
+                    write!(&mut hex_hard, "{:x}", byte).unwrap();
+                }
+                writeln!(&mut external_documents_ids, "hard: {hex_hard}").unwrap();
+
+                snapshot_string!(external_documents_ids);
+            }
+            {
+                let mut snap = String::new();
+                for field_id in fields_ids_map.ids() {
+                    let number_faceted_documents_ids =
+                        index.number_faceted_documents_ids(&rtxn, field_id).unwrap();
+                    writeln!(
+                        &mut snap,
+                        "{field_id:<3} {}",
+                        display_bitmap(&number_faceted_documents_ids)
+                    )
+                    .unwrap();
+                }
+                let number_faceted_documents_ids = snap;
+                snapshot_string!(number_faceted_documents_ids);
+            }
+            {
+                let mut snap = String::new();
+                for field_id in fields_ids_map.ids() {
+                    let string_faceted_documents_ids =
+                        index.string_faceted_documents_ids(&rtxn, field_id).unwrap();
+                    writeln!(
+                        &mut snap,
+                        "{field_id:<3} {}",
+                        display_bitmap(&string_faceted_documents_ids)
+                    )
+                    .unwrap();
+                }
+                let string_faceted_documents_ids = snap;
+                snapshot_string!(string_faceted_documents_ids);
+            }
+            {
+                let words_fst = index.words_fst(&rtxn).unwrap();
+                let bytes = words_fst.into_fst().as_bytes().to_owned();
+                let mut words_fst = String::new();
+                for byte in bytes {
+                    write!(&mut words_fst, "{:x}", byte).unwrap();
+                }
+                snapshot_string!(words_fst);
+            }
+            {
+                let words_prefixes_fst = index.words_prefixes_fst(&rtxn).unwrap();
+                let bytes = words_prefixes_fst.into_fst().as_bytes().to_owned();
+                let mut words_prefixes_fst = String::new();
+                for byte in bytes {
+                    write!(&mut words_prefixes_fst, "{:x}", byte).unwrap();
+                }
+                snapshot_string!(words_prefixes_fst);
+            }
+        }
+    });
+}