diff --git a/app.yml b/app.yml
index ca7c321..f82747f 100644
--- a/app.yml
+++ b/app.yml
@@ -23,6 +23,12 @@ webDiffServers:
 #    file2: https://wotwizard2.cgeek.fr/WWMeta.json
 #    frequency: 60000
 
+headServers:
+  - address: https://g1.cgeek.fr
+    frequency: 60000 # 1'
+    maxLateBlocks: 3
+    observedPubkey: A5LQXCkx8b6rzppfqdqeHbKPDGmKZtRcqwxP4BSeag5r
+
 mail:
   enabled: false
   host: smtp.sparkpostmail.com
diff --git a/src/lib/types/conf.ts b/src/lib/types/conf.ts
index 7af98b5..db460e4 100644
--- a/src/lib/types/conf.ts
+++ b/src/lib/types/conf.ts
@@ -5,6 +5,7 @@ export interface Conf {
   bmaServers: ConfBMA[]
   dprobeHeartbeats: ConfDprobeHeartbeat[]
   webDiffServers: ConfWebDiff[]
+  headServers: ConfHead[]
   mail: ConfMail
 }
 
@@ -33,6 +34,11 @@ export interface ConfBMA extends ConfURL {
   maxLate?: number
 }
 
+export interface ConfHead extends ConfURL {
+  observedPubkey: string
+  maxLateBlocks: number
+}
+
 export interface ConfDprobeHeartbeat extends ConfURL{
   lastBeat: number
 }
diff --git a/src/lib/watchers/bma/head-watcher.ts b/src/lib/watchers/bma/head-watcher.ts
new file mode 100644
index 0000000..47c1787
--- /dev/null
+++ b/src/lib/watchers/bma/head-watcher.ts
@@ -0,0 +1,104 @@
+import {Conf, ConfHead} from "../../types/conf";
+import {urlWatcher} from '../abstract/url-watcher'
+import {WS2PHead} from "duniter/app/modules/ws2p/lib/WS2PCluster";
+
+function handleLateness(confHead: ConfHead, mainHeads: HeadMetric[], observedHead?: TrameWS2P) {
+  if (!mainHeads.length) {
+    throw 'No consensus found'
+  }
+  if (!observedHead) {
+    throw `Observed pubkey ${confHead.observedPubkey} not found in heads`
+  }
+  const matchingHeads = mainHeads.filter(h => h.blockstamp === observedHead.blockstamp)
+  if (!matchingHeads.length) {
+    // Check how much late is the node
+    const farAwayHeads = mainHeads.filter(h => h.blockNumber - observedHead.blockNumber >= confHead.maxLateBlocks)
+    if (farAwayHeads.length) {
+      throw `Observed pubkey is too late for ${farAwayHeads.length} consensus by at least ${confHead.maxLateBlocks}`
+    }
+  }
+}
+
+export function headWatcher(conf: Conf) {
+
+  const URL_PATH = '/network/ws2p/heads'
+
+  return async (confHead: ConfHead) => {
+
+    return urlWatcher(conf, async (data) => {
+      const heads = data as { heads: WS2PHead[] }
+      const mainHeads = getMain(heads)
+      const observedHead = getObserved(heads, confHead.observedPubkey)
+      handleLateness(confHead, mainHeads, observedHead)
+    })({
+      name: `head watcher ${confHead.address}`,
+      address: confHead.address + URL_PATH,
+      frequency: confHead.frequency
+    })
+  }
+}
+
+function getMain(heads: { heads: WS2PHead[] }): HeadMetric[] {
+  const mapByHash: { [k: string]: HeadMetric } = {}
+  for (const head of heads.heads) {
+    const trame = getTrame(head)
+    if (trame) {
+      mapByHash[trame.blockstamp] = mapByHash[trame.blockstamp] || { pubkeys: [], blockNumber: trame.blockNumber, blockstamp: trame.blockstamp }
+      mapByHash[trame.blockstamp].pubkeys.push(trame.pubkey)
+    }
+    else {
+      console.warn('Pas de trame pour %s', head)
+    }
+  }
+  return Object.keys(mapByHash).reduce((main, blockstamp) => {
+    const newMetric = mapByHash[blockstamp]
+    if (!main.length) {
+      return [newMetric]
+    }
+    const newMain: HeadMetric[] = main.filter(m => m.pubkeys.length >= newMetric.pubkeys.length)
+    let maxLen = main.length ? main[0].pubkeys.length : newMetric.pubkeys.length
+    if (newMetric.pubkeys.length >= maxLen) {
+      newMain.push(newMetric)
+    }
+    return newMain
+  }, [] as HeadMetric[])
+}
+
+function getObserved(heads: { heads: WS2PHead[] }, observedPubkey: string): TrameWS2P|undefined {
+  const trame = heads.heads
+      .map(getTrame)
+      .filter(trame =>  trame && trame.pubkey === observedPubkey)[0]
+  if (!trame) {
+    return undefined
+  }
+  return trame
+}
+
+function getTrame(head: WS2PHead): TrameWS2P|undefined {
+  if (head.messageV2) {
+    const [ protocol, type, trameVersion, pubkey, blockstamp, peerUuid, software, softVersion, n1, n2, n3 ] = head.messageV2.split(':')
+    const [ blockNumber, blockHash ] = blockstamp.split('-')
+    return { pubkey, blockstamp, blockNumber: parseInt(blockNumber), blockHash }
+  }
+  else if (head.message) {
+    const [ protocol, type, trameVersion, pubkey, blockstamp, peerUuid, software, softVersion, n1 ] = head.message.split(':')
+    const [ blockNumber, blockHash ] = blockstamp.split('-')
+    return { pubkey, blockstamp, blockNumber: parseInt(blockNumber), blockHash }
+  }
+  else {
+    return undefined
+  }
+}
+
+interface HeadMetric {
+  pubkeys: string[]
+  blockstamp: string
+  blockNumber: number
+}
+
+interface TrameWS2P {
+  pubkey: string
+  blockstamp: string
+  blockNumber: number
+  blockHash: string
+}
\ No newline at end of file