diff --git a/Cargo.lock b/Cargo.lock
index 94aea9e2a..f0ebc2ff6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -79,12 +79,12 @@ dependencies = [
 
 [[package]]
 name = "atty"
-version = "0.2.14"
+version = "0.2.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d9b39be18770d11421cdb1b9947a45dd3f37e93092cbf377614828a319d5fee8"
+checksum = "9a7d5b8723950951411ee34d271d99dddcc2035a16ab25310ea2c8cfd4369652"
 dependencies = [
- "hermit-abi",
  "libc",
+ "termion",
  "winapi 0.3.8",
 ]
 
@@ -164,7 +164,7 @@ version = "0.2.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "31accafdb70df7871592c058eca3985b71104e15ac32f64706022c58867da931"
 dependencies = [
- "lazy_static",
+ "lazy_static 1.4.0",
  "memchr",
  "regex-automata",
  "serde",
@@ -228,6 +228,17 @@ version = "0.1.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "4785bdd1c96b2a846b2bd7cc02e86b6b3dbf14e7e53446c4f54c92a361040822"
 
+[[package]]
+name = "chrono"
+version = "0.4.13"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c74d84029116787153e02106bf53e66828452a4b325cc8652b788b5967c0a0b6"
+dependencies = [
+ "num-integer",
+ "num-traits",
+ "time",
+]
+
 [[package]]
 name = "clap"
 version = "2.33.1"
@@ -281,7 +292,7 @@ dependencies = [
  "criterion-plot",
  "csv",
  "itertools",
- "lazy_static",
+ "lazy_static 1.4.0",
  "num-traits",
  "oorandom",
  "plotters",
@@ -324,7 +335,7 @@ dependencies = [
  "autocfg 1.0.0",
  "cfg-if",
  "crossbeam-utils",
- "lazy_static",
+ "lazy_static 1.4.0",
  "maybe-uninit",
  "memoffset",
  "scopeguard",
@@ -348,7 +359,7 @@ checksum = "c3c7c73a2d1e9fc0886a08b93e98eb643461230d5f1925e4036204d5f2e261a8"
 dependencies = [
  "autocfg 1.0.0",
  "cfg-if",
- "lazy_static",
+ "lazy_static 1.4.0",
 ]
 
 [[package]]
@@ -845,6 +856,12 @@ dependencies = [
  "winapi-build",
 ]
 
+[[package]]
+name = "lazy_static"
+version = "0.2.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "76f033c7ad61445c5b347c7382dd1237847eb1bce590fe50365dcb33d546be73"
+
 [[package]]
 name = "lazy_static"
 version = "1.4.0"
@@ -951,6 +968,7 @@ dependencies = [
  "itertools",
  "jemallocator",
  "levenshtein_automata",
+ "log 0.4.8",
  "memmap",
  "once_cell",
  "oxidized-mtbl",
@@ -960,6 +978,7 @@ dependencies = [
  "slice-group-by",
  "smallstr",
  "smallvec",
+ "stderrlog",
  "structopt",
  "tempfile",
  "tokio",
@@ -1115,6 +1134,16 @@ dependencies = [
  "version_check 0.9.2",
 ]
 
+[[package]]
+name = "num-integer"
+version = "0.1.43"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8d59457e662d541ba17869cf51cf177c0b5f0cbf476c66bdc90bf1edac4f875b"
+dependencies = [
+ "autocfg 1.0.0",
+ "num-traits",
+]
+
 [[package]]
 name = "num-traits"
 version = "0.2.12"
@@ -1134,6 +1163,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "numtoa"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b8f8bdf33df195859076e54ab11ee78a1b208382d3a26ec40d142ffc1ecc49ef"
+
 [[package]]
 name = "once_cell"
 version = "1.4.0"
@@ -1505,7 +1540,7 @@ dependencies = [
  "crossbeam-deque",
  "crossbeam-queue",
  "crossbeam-utils",
- "lazy_static",
+ "lazy_static 1.4.0",
  "num_cpus",
 ]
 
@@ -1524,6 +1559,15 @@ version = "0.1.56"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2439c63f3f6139d1b57529d16bc3b8bb855230c8efcc5d3a896c8bea7c3b1e84"
 
+[[package]]
+name = "redox_termios"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7e891cfe48e9100a70a3b6eb652fef28920c117d366339687bd5576160db0f76"
+dependencies = [
+ "redox_syscall",
+]
+
 [[package]]
 name = "regex"
 version = "1.3.9"
@@ -1738,6 +1782,19 @@ dependencies = [
  "winapi 0.3.8",
 ]
 
+[[package]]
+name = "stderrlog"
+version = "0.4.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "32e5ee9b90a5452c570a0b0ac1c99ae9498db7e56e33d74366de7f2a7add7f25"
+dependencies = [
+ "atty",
+ "chrono",
+ "log 0.4.8",
+ "termcolor",
+ "thread_local",
+]
+
 [[package]]
 name = "structopt"
 version = "0.3.14"
@@ -1745,7 +1802,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "863246aaf5ddd0d6928dfeb1a9ca65f505599e4e1b399935ef7e75107516b4ef"
 dependencies = [
  "clap",
- "lazy_static",
+ "lazy_static 1.4.0",
  "structopt-derive",
 ]
 
@@ -1810,6 +1867,27 @@ dependencies = [
  "winapi 0.3.8",
 ]
 
+[[package]]
+name = "termcolor"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bb6bfa289a4d7c5766392812c0a1f4c1ba45afa1ad47803c11e1f407d846d75f"
+dependencies = [
+ "winapi-util",
+]
+
+[[package]]
+name = "termion"
+version = "1.5.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c22cec9d8978d906be5ac94bceb5a010d885c626c4c8855721a4dbd20e3ac905"
+dependencies = [
+ "libc",
+ "numtoa",
+ "redox_syscall",
+ "redox_termios",
+]
+
 [[package]]
 name = "textwrap"
 version = "0.11.0"
@@ -1819,6 +1897,16 @@ dependencies = [
  "unicode-width",
 ]
 
+[[package]]
+name = "thread_local"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1697c4b57aeeb7a536b647165a2825faddffb1d3bad386d507709bd51a90bb14"
+dependencies = [
+ "lazy_static 0.2.11",
+ "unreachable",
+]
+
 [[package]]
 name = "time"
 version = "0.1.43"
@@ -1849,7 +1937,7 @@ dependencies = [
  "fnv",
  "futures-core",
  "iovec",
- "lazy_static",
+ "lazy_static 1.4.0",
  "libc",
  "memchr",
  "mio",
@@ -2010,6 +2098,15 @@ version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "826e7639553986605ec5979c7dd957c7895e93eabed50ab2ffa7f6128a75097c"
 
+[[package]]
+name = "unreachable"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "382810877fe448991dfc7f0dd6e3ae5d58088fd0ea5e35189655f84e6814fa56"
+dependencies = [
+ "void",
+]
+
 [[package]]
 name = "url"
 version = "2.1.1"
@@ -2045,6 +2142,12 @@ version = "0.9.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b5a972e5669d67ba988ce3dc826706fb0a8b01471c088cb0b6110b805cc36aed"
 
+[[package]]
+name = "void"
+version = "1.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6a02e4885ed3bc0f2de90ea6dd45ebcbb66dacffe03547fadbb0eeae2770887d"
+
 [[package]]
 name = "walkdir"
 version = "2.3.1"
@@ -2115,7 +2218,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ded84f06e0ed21499f6184df0e0cb3494727b0c5da89534e0fcc55c51d812101"
 dependencies = [
  "bumpalo",
- "lazy_static",
+ "lazy_static 1.4.0",
  "log 0.4.8",
  "proc-macro2",
  "quote",
diff --git a/Cargo.toml b/Cargo.toml
index 5d62757e4..4a991436f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -27,6 +27,10 @@ smallvec = "1.4.0"
 structopt = { version = "0.3.14", default-features = false }
 tempfile = "3.1.0"
 
+# logging
+log = "0.4.8"
+stderrlog = "0.4.3"
+
 # best proximity
 indexmap = "1.4.0"
 
diff --git a/src/best_proximity.rs b/src/best_proximity.rs
index cb6302a16..6dda4d1fb 100644
--- a/src/best_proximity.rs
+++ b/src/best_proximity.rs
@@ -1,6 +1,7 @@
 use std::cmp;
 use std::time::Instant;
 
+use log::debug;
 use crate::iter_shortest_paths::astar_bag;
 
 const ONE_ATTRIBUTE: u32 = 1000;
@@ -153,18 +154,18 @@ impl BestProximity {
             },
         );
 
-        eprintln!("BestProximity::next() took {:.02?}", before.elapsed());
+        debug!("BestProximity::next() took {:.02?}", before.elapsed());
 
         match result {
             Some((paths, proximity)) => {
                 self.best_proximity = proximity + 1;
                 // We retrieve the last path that we convert into a Vec
                 let paths: Vec<_> = paths.map(|p| p.iter().filter_map(Node::position).collect()).collect();
-                eprintln!("result: {} {:?}", proximity, paths);
+                debug!("result: {} {:?}", proximity, paths);
                 Some((proximity, paths))
             },
             None => {
-                eprintln!("result: {:?}", None as Option<()>);
+                debug!("result: {:?}", None as Option<()>);
                 self.best_proximity += 1;
                 None
             },
diff --git a/src/bin/indexer.rs b/src/bin/indexer.rs
index a9191b618..6f490fae7 100644
--- a/src/bin/indexer.rs
+++ b/src/bin/indexer.rs
@@ -11,6 +11,7 @@ use cow_utils::CowUtils;
 use fst::{Streamer, IntoStreamer};
 use heed::EnvOpenOptions;
 use heed::types::*;
+use log::debug;
 use oxidized_mtbl::{Reader, ReaderOptions, Writer, Merger, MergerOptions};
 use rayon::prelude::*;
 use roaring::RoaringBitmap;
@@ -86,7 +87,7 @@ struct MtblKvStore(Option<File>);
 
 impl MtblKvStore {
     fn from_indexed(mut indexed: Indexed) -> anyhow::Result<MtblKvStore> {
-        eprintln!("Creating an MTBL store from an Indexed...");
+        debug!("Creating an MTBL store from an Indexed...");
 
         let outfile = tempfile::tempfile()?;
         let mut out = Writer::new(outfile, None)?;
@@ -152,7 +153,7 @@ impl MtblKvStore {
 
         let out = out.into_inner()?;
 
-        eprintln!("MTBL store created!");
+        debug!("MTBL store created!");
         Ok(MtblKvStore(Some(out)))
     }
 
@@ -198,7 +199,7 @@ impl MtblKvStore {
     fn from_many<F>(stores: Vec<MtblKvStore>, mut f: F) -> anyhow::Result<()>
     where F: FnMut(&[u8], &[u8]) -> anyhow::Result<()>
     {
-        eprintln!("Merging {} MTBL stores...", stores.len());
+        debug!("Merging {} MTBL stores...", stores.len());
         let before = Instant::now();
 
         let mmaps: Vec<_> = stores.iter().flat_map(|m| {
@@ -217,7 +218,7 @@ impl MtblKvStore {
             (f)(k, v)?;
         }
 
-        eprintln!("MTBL stores merged in {:.02?}!", before.elapsed());
+        debug!("MTBL stores merged in {:.02?}!", before.elapsed());
         Ok(())
     }
 }
@@ -256,7 +257,7 @@ fn index_csv(
     max_mem_usage: usize,
 ) -> anyhow::Result<Vec<MtblKvStore>>
 {
-    eprintln!("{:?}: Indexing into an Indexed...", thread_index);
+    debug!("{:?}: Indexing into an Indexed...", thread_index);
 
     let mut stores = Vec::new();
 
@@ -281,7 +282,7 @@ fn index_csv(
         let document_id = DocumentId::try_from(document_id).context("generated id is too big")?;
 
         if document_id % (ONE_MILLION as u32) == 0 {
-            eprintln!("We have seen {}m documents so far.", document_id / ONE_MILLION as u32);
+            debug!("We have seen {}m documents so far.", document_id / ONE_MILLION as u32);
         }
 
         for (attr, content) in document.iter().enumerate().take(MAX_ATTRIBUTES) {
@@ -310,21 +311,21 @@ fn index_csv(
         if documents.len() % 100_000 == 0 {
             let usage = mem_usage(&word_positions, &word_position_docids, &documents);
             if usage > max_mem_usage {
-                eprintln!("Whoops too much memory used ({}B).", usage);
+                debug!("Whoops too much memory used ({}B).", usage);
 
                 let word_positions = mem::take(&mut word_positions);
                 let word_position_docids = mem::take(&mut word_position_docids);
                 let documents = mem::take(&mut documents);
 
                 let indexed = Indexed::new(word_positions, word_position_docids, headers.clone(), documents)?;
-                eprintln!("{:?}: Indexed created!", thread_index);
+                debug!("{:?}: Indexed created!", thread_index);
                 stores.push(MtblKvStore::from_indexed(indexed)?);
             }
         }
     }
 
     let indexed = Indexed::new(word_positions, word_position_docids, headers, documents)?;
-    eprintln!("{:?}: Indexed created!", thread_index);
+    debug!("{:?}: Indexed created!", thread_index);
     stores.push(MtblKvStore::from_indexed(indexed)?);
 
     Ok(stores)
@@ -372,7 +373,7 @@ fn writer(wtxn: &mut heed::RwTxn, index: &Index, key: &[u8], val: &[u8]) -> anyh
 fn compute_words_attributes_docids(wtxn: &mut heed::RwTxn, index: &Index) -> anyhow::Result<()> {
     let before = Instant::now();
 
-    eprintln!("Computing the attributes documents ids...");
+    debug!("Computing the attributes documents ids...");
 
     let fst = match index.fst(&wtxn)? {
         Some(fst) => fst.map_data(|s| s.to_vec())?,
@@ -408,7 +409,7 @@ fn compute_words_attributes_docids(wtxn: &mut heed::RwTxn, index: &Index) -> any
         }
     }
 
-    eprintln!("Computing the attributes documents ids took {:.02?}.", before.elapsed());
+    debug!("Computing the attributes documents ids took {:.02?}.", before.elapsed());
 
     Ok(())
 }
@@ -444,7 +445,7 @@ fn main() -> anyhow::Result<()> {
 
     let stores: Vec<_> = stores.into_iter().flatten().collect();
 
-    eprintln!("We are writing into LMDB...");
+    debug!("We are writing into LMDB...");
     let mut wtxn = env.write_txn()?;
 
     MtblKvStore::from_many(stores, |k, v| writer(&mut wtxn, &index, k, v))?;
@@ -452,7 +453,7 @@ fn main() -> anyhow::Result<()> {
     let count = index.documents.len(&wtxn)?;
 
     wtxn.commit()?;
-    eprintln!("Wrote {} documents into LMDB", count);
+    debug!("Wrote {} documents into LMDB", count);
 
     Ok(())
 }
diff --git a/src/bin/search.rs b/src/bin/search.rs
index 5f5d458f4..92112826a 100644
--- a/src/bin/search.rs
+++ b/src/bin/search.rs
@@ -4,8 +4,9 @@ use std::path::PathBuf;
 use std::time::Instant;
 
 use heed::EnvOpenOptions;
-use structopt::StructOpt;
+use log::debug;
 use milli::{Index, BEU32};
+use structopt::StructOpt;
 
 #[cfg(target_os = "linux")]
 #[global_allocator]
@@ -62,7 +63,7 @@ fn main() -> anyhow::Result<()> {
             }
         }
 
-        eprintln!("Took {:.02?} to find {} documents", before.elapsed(), documents_ids.len());
+        debug!("Took {:.02?} to find {} documents", before.elapsed(), documents_ids.len());
     }
 
     Ok(())
diff --git a/src/bin/serve.rs b/src/bin/serve.rs
index 387c26d1b..9d4ae77d1 100644
--- a/src/bin/serve.rs
+++ b/src/bin/serve.rs
@@ -158,7 +158,7 @@ async fn main() -> anyhow::Result<()> {
         .or(query_route);
 
     let addr = SocketAddr::from_str(&opt.http_listen_addr).unwrap();
-    eprintln!("listening on http://{}", addr);
+    println!("listening on http://{}", addr);
     warp::serve(routes).run(addr).await;
 
     Ok(())
diff --git a/src/lib.rs b/src/lib.rs
index 9d1240a1a..fad74976f 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -14,6 +14,7 @@ use fxhash::{FxHasher32, FxHasher64};
 use heed::types::*;
 use heed::{PolyDatabase, Database};
 use levenshtein_automata::LevenshteinAutomatonBuilder as LevBuilder;
+use log::debug;
 use once_cell::sync::Lazy;
 use roaring::RoaringBitmap;
 
@@ -138,7 +139,7 @@ impl Index {
                 }
             }
 
-            eprintln!("{} words for {:?} we have found positions {:?} in {:.02?}",
+            debug!("{} words for {:?} we have found positions {:?} in {:.02?}",
                 count, word, union_positions, before.elapsed());
             words.push(derived_words);
             positions.push(union_positions.iter().collect());
@@ -168,9 +169,9 @@ impl Index {
             words_attributes_docids.push(intersect_docids);
         }
 
-        eprintln!("The documents you must find for each attribute: {:?}", words_attributes_docids);
+        debug!("The documents you must find for each attribute: {:?}", words_attributes_docids);
 
-        eprintln!("Retrieving words positions took {:.02?}", before.elapsed());
+        debug!("Retrieving words positions took {:.02?}", before.elapsed());
 
         // Returns the union of the same position for all the derived words.
         let unions_word_pos = |word: usize, pos: u32| {
@@ -259,10 +260,10 @@ impl Index {
                         }
                     });
 
-                eprintln!("retrieving words took {:.02?} and took {:.02?} to intersect",
+                debug!("retrieving words took {:.02?} and took {:.02?} to intersect",
                     elapsed_retrieving, before_intersect.elapsed());
 
-                eprintln!("for proximity {:?} {:?} we took {:.02?} to find {} documents",
+                debug!("for proximity {:?} {:?} we took {:.02?} to find {} documents",
                     proximity, positions, before.elapsed(),
                     intersect_docids.as_ref().map_or(0, |rb| rb.len()));
 
@@ -272,7 +273,7 @@ impl Index {
 
                 // We found enough documents we can stop here
                 if documents.iter().map(RoaringBitmap::len).sum::<u64>() + same_proximity_union.len() >= 20 {
-                    eprintln!("proximity {} took a total of {:.02?}", proximity, same_prox_before.elapsed());
+                    debug!("proximity {} took a total of {:.02?}", proximity, same_prox_before.elapsed());
                     break;
                 }
             }
@@ -294,8 +295,8 @@ impl Index {
             }
             documents.retain(|rb| !rb.is_empty());
 
-            eprintln!("documents: {:?}", documents);
-            eprintln!("proximity {} took a total of {:.02?}", proximity, same_prox_before.elapsed());
+            debug!("documents: {:?}", documents);
+            debug!("proximity {} took a total of {:.02?}", proximity, same_prox_before.elapsed());
 
             // We found enough documents we can stop here.
             if documents.iter().map(RoaringBitmap::len).sum::<u64>() >= 20 {
@@ -303,7 +304,7 @@ impl Index {
             }
         }
 
-        eprintln!("{} candidates", documents.iter().map(RoaringBitmap::len).sum::<u64>());
+        debug!("{} candidates", documents.iter().map(RoaringBitmap::len).sum::<u64>());
         Ok(documents.iter().flatten().take(20).collect())
     }
 }