diff --git a/xwords4/wasm/Makefile b/xwords4/wasm/Makefile
index 1b410b991..a6d3fefd1 100644
--- a/xwords4/wasm/Makefile
+++ b/xwords4/wasm/Makefile
@@ -46,6 +46,7 @@ DEFINES += -DXWFEATURE_STREAMREF
 DEFINES += -DNATIVE_NLI
 DEFINES += -DDEBUG_REF
 DEFINES += -Wno-switch
+DEFINES += -DGITREV=\"$(shell git describe --tags --dirty)\"
 
 ifeq ($(MEMDEBUG),TRUE)
 	DEFINES += -DMEM_DEBUG -DDEBUG -O0
diff --git a/xwords4/wasm/main.c b/xwords4/wasm/main.c
index 10419cd6e..904c45bde 100644
--- a/xwords4/wasm/main.c
+++ b/xwords4/wasm/main.c
@@ -156,9 +156,11 @@ EM_JS(void, call_get_string, (const char* msg, const char* dflt,
           nbGetString( jsMgs, jsDflt, proc, closure );
       } );
 
-EM_JS(void, call_haveDevID, (void* closure, const char* devid, StringProc proc), {
-        onHaveDevID(closure, UTF8ToString(devid), proc);
-});
+EM_JS(void, call_haveDevID, (void* closure, const char* devid,
+                             const char* gitrev, int now, StringProc proc), {
+          let jsgr = UTF8ToString(gitrev);
+          onHaveDevID(closure, UTF8ToString(devid), jsgr, now, proc);
+      });
 
 EM_JS(bool, call_mqttSend, (const char* topic, const uint8_t* ptr, int len), {
         let topStr = UTF8ToString(topic);
@@ -550,7 +552,8 @@ initDeviceGlobals( Globals* globals )
     XP_UCHAR buf[32];
     XP_SNPRINTF( buf, VSIZE(buf), MQTTDevID_FMT, devID );
     XP_LOGFF( "got mqtt devID: %s", buf );
-    call_haveDevID( globals, buf, onConflict );
+    int now = dutil_getCurSeconds( globals->dutil, NULL );
+    call_haveDevID( globals, buf, GITREV, now, onConflict );
 }
 
 static void
diff --git a/xwords4/wasm/xwutils.js b/xwords4/wasm/xwutils.js
index b13336ac9..b89dfbb93 100644
--- a/xwords4/wasm/xwutils.js
+++ b/xwords4/wasm/xwutils.js
@@ -8,7 +8,46 @@ function ccallString(proc, closure, str) {
 				 [proc, closure, str]);
 }
 
-function onHaveDevID(closure, devid, proc) {
+function registerOnce(devid, gitrev, now) {
+	let nextTimeKey = 'next_reg';
+	let gitKey = 'last_write';
+	let nextTime = localStorage.getItem(nextTimeKey);
+	let prevGit = localStorage.getItem(gitKey);
+	// false: for now, always register. PENDING
+	if ( false && prevGit == gitrev && now < nextTime ) {
+		// console.log("registerOnce: skipping");
+	} else {
+		let args = { devid: devid,
+					 gitrev: gitrev,
+					 loc: navigator.language,
+					 os: navigator.appName,
+					 vers: '0.0',
+					 dbg: true,
+					 myNow: now,
+					 vrntName: 'wasm',
+				   };
+		let body = JSON.stringify(args);
+		// console.log('registerOnce(): args: ' + body);
+
+		fetch('/xw4/api/v1/register', {
+			method: 'post',
+			body: body,
+			headers: {
+				'Content-Type': 'application/json'
+			},
+		}).then(res => {
+			return res.json();
+		}).then(data => {
+			console.log('data: ' + JSON.stringify(data));
+			if ( data.success ) {
+				localStorage.setItem(nextTimeKey, data.atNext);
+				localStorage.setItem(gitKey, gitrev);
+			}
+		});
+	}
+}
+
+function onHaveDevID(closure, devid, gitrev, now, proc) {
 	// Set a unique tag so we know if somebody comes along later
 	let tabID = Math.random();
 	localStorage.setItem('tabID', tabID);
@@ -22,6 +61,8 @@ function onHaveDevID(closure, devid, proc) {
 	};
 	window.addEventListener('storage', listener);
 
+	registerOnce(devid, gitrev, now);
+
 	state.closure = closure;
 	document.getElementById("mqtt_span").textContent=devid;