diff --git a/README.md b/README.md
index 70c4c5a..5776bb4 100644
--- a/README.md
+++ b/README.md
@@ -47,7 +47,9 @@ Depending on the sources you'll be using to generate the list, you'll need to in
 ### Create a new database
 
 The so-called database (in the form of `blocking.p`) is a file storing all the matching entities (ASN, IPs, hostnames, zones…) and every entity leading to it.
-For now there's no way to remove data from it, so here's the command to recreate it: `./db.py --initialize`.
+It exists because the list cannot be generated in one pass, as DNS redirections chain links do not have to be inputed in order.
+You can purge the database by removing old data using `./db.py --prune --prune-before TIMESTAMP` ;
+`TIMESTAMP` can be generated using `date +%s`.
 
 ### Gather external sources
 
@@ -79,6 +81,7 @@ In each folder:
 - `*.custom.ext` are for sources that you don't want commited
 
 Then, run `./import_rules.sh`.
+Note that removed rules and every record depending on them will be automatically pruned.
 
 ### Add subdomains
 
diff --git a/database.py b/database.py
index c37369f..866eb66 100644
--- a/database.py
+++ b/database.py
@@ -95,6 +95,9 @@ class Match():
             return False
         return True
 
+    def disable(self) -> None:
+        self.updated = 0
+
 
 class AsnNode(Match):
     def __init__(self) -> None:
@@ -478,15 +481,61 @@ class Database(Profiler):
         for _ in self.exec_each(increment_references_cb):
             pass
 
+    def _clean_deps(self) -> None:
+        # Disable the matches that depends on the targeted
+        # matches until all disabled matches reference count = 0
+        did_something = True
+
+        def clean_deps_cb(path: Path,
+                          match: Match
+                          ) -> None:
+            nonlocal did_something
+            if not match.source:
+                return
+            source = self.get_match(match.source)
+            if not source.active():
+                self._unset_match(match)
+            elif match.first_party > source.first_party:
+                match.first_party = source.first_party
+            else:
+                return
+            did_something = True
+
+        while did_something:
+            did_something = False
+            self.enter_step('pass_clean_deps')
+            for _ in self.exec_each(clean_deps_cb):
+                pass
+
     def prune(self, before: int, base_only: bool = False) -> None:
-        raise NotImplementedError
+        # Disable the matches targeted
+        def prune_cb(path: Path,
+                     match: Match
+                     ) -> None:
+            if base_only and match.level > 1:
+                return
+            if match.updated > before:
+                return
+            self._unset_match(match)
+            self.log.debug("Print: disabled %s", path)
+
+        self.enter_step('pass_prune')
+        for _ in self.exec_each(prune_cb):
+            pass
+
+        self._clean_deps()
+
+        # Remove branches with no match
+        # TODO
 
     def explain(self, path: Path) -> str:
         match = self.get_match(path)
+        string = str(path)
         if isinstance(match, AsnNode):
-            string = f'{path} ({match.name}) #{match.references}'
-        else:
-            string = f'{path} #{match.references}'
+            string += f' ({match.name})'
+        party_char = 'F' if match.first_party else 'M'
+        dup_char = 'D' if match.dupplicate else '_'
+        string += f' {match.level}{party_char}{dup_char}{match.references}'
         if match.source:
             string += f' ← {self.explain(match.source)}'
         return string
@@ -598,6 +647,14 @@ class Database(Profiler):
             self.enter_step('get_ip4_yield')
             yield ip4
 
+    def _unset_match(self,
+                     match: Match,
+                     ) -> None:
+        match.disable()
+        if match.source:
+            source_match = self.get_match(match.source)
+            source_match.references -= 1
+
     def _set_match(self,
                    match: Match,
                    updated: int,
diff --git a/import_rules.sh b/import_rules.sh
index cbcfbd8..14c8c78 100755
--- a/import_rules.sh
+++ b/import_rules.sh
@@ -18,5 +18,5 @@ cat rules_asn/first-party.txt | grep -v '^#' | grep -v '^$' | ./feed_rules.py as
 
 ./feed_asn.py
 
-# log "Pruning old rules…"
-# ./db.py --prune --prune-before "$BEFORE" --prune-base
+log "Pruning old rules…"
+./db.py --prune --prune-before "$BEFORE" --prune-base
diff --git a/resolve_subdomains.sh b/resolve_subdomains.sh
index 7a91337..b5b2079 100755
--- a/resolve_subdomains.sh
+++ b/resolve_subdomains.sh
@@ -7,7 +7,7 @@ function log() {
 log "Compiling nameservers…"
 pv nameservers/*.list | ./validate_list.py --ip4 | sort -u > temp/all_nameservers_ip4.list
 
-log "Compiling subdomain…"
+log "Compiling subdomains…"
 # Sort by last character to utilize the DNS server caching mechanism
 # (not as efficient with massdns but it's almost free so why not)
 pv subdomains/*.list | ./validate_list.py --domain | rev | sort -u | rev > temp/all_subdomains.list