diff --git a/lib/http-worker.js b/lib/http-worker.js
index 8e3a10187..995bcdd7e 100644
--- a/lib/http-worker.js
+++ b/lib/http-worker.js
@@ -9,6 +9,7 @@ const Logger = require("./log");
 const AuthCommands = require("./http-commands");
 const MFA = require("./storage/mfa");
 const Sessions = require("./storage/sessions");
+const BlobStore = require("./storage/blob");
 
 const DEFAULT_QUERY_TIMEOUT = 5000;
 const PID = process.pid;
@@ -206,6 +207,13 @@ app.use('/blob', function (req, res, next) {
 /*  Head requests are used to check the size of a blob.
     Clients can configure a maximum size to download automatically,
     and can manually click to download blobs which exceed that limit.  */
+    const url = req.url;
+    if (typeof(url) === "string" && Env.blobStore) {
+        const s = url.split('/');
+        if (s[1] && s[1].length === 2 && s[2] && s[2].length === Env.blobStore.BLOB_LENGTH) {
+            Env.blobStore.updateActivity(s[2], () => {});
+        }
+    }
     if (req.method === 'HEAD') {
         Express.static(Path.resolve(Env.paths.blob), {
             setHeaders: function (res /*, path, stat */) {
@@ -618,6 +626,17 @@ nThen(function (w) {
         // websocket traffic to the correct port (Env.websocketPort)
         wsProxy.upgrade(req, socket, head);
     });
+
+    var config = require("./load-config");
+    BlobStore.create({
+        blobPath: config.blobPath,
+        blobStagingPath: config.blobStagingPath,
+        archivePath: config.archivePath,
+        getSession: function () {},
+    }, w(function (err, blob) {
+        if (err) { return; }
+        Env.blobStore = blob;
+    }));
 }).nThen(function () {
     // TODO inform the parent process that this worker is ready
 
diff --git a/lib/storage/blob.js b/lib/storage/blob.js
index 7d55676d7..38d4a906f 100644
--- a/lib/storage/blob.js
+++ b/lib/storage/blob.js
@@ -8,12 +8,14 @@ var nThen = require("nthen");
 var Semaphore = require("saferphore");
 var Util = require("../common-util");
 
+const BLOB_LENGTH = 48;
+
 var isValidSafeKey = function (safeKey) {
     return typeof(safeKey) === 'string' && !/\//.test(safeKey) && safeKey.length === 44;
 };
 
 var isValidId = function (id) {
-    return typeof(id) === 'string' && id.length === 48 && !/[^a-f0-9]/.test(id);
+    return typeof(id) === 'string' && id.length === BLOB_LENGTH && !/[^a-f0-9]/.test(id);
 };
 
 // helpers
@@ -31,6 +33,10 @@ var makeBlobPath = function (Env, blobId) {
     return Path.join(Env.blobPath, blobId.slice(0, 2), blobId);
 };
 
+var makeActivityPath = function (Env, blobId) {
+    return makeBlobPath(Env, blobId) + '.activity';
+};
+
 // /blobstate/<safeKeyPrefix>/<safeKey>
 var makeStagePath = function (Env, safeKey) {
     return Path.join(Env.blobStagingPath, safeKey.slice(0, 2), safeKey);
@@ -103,6 +109,31 @@ var makeFileStream = function (full, _cb) {
     });
 };
 
+var clearActivity = function (Env, blobId, cb) {
+    var path = makeActivityPath(Env, blobId);
+    // if we fail to delete the activity file, it can still be removed later by the eviction script
+    Fs.unlink(path, cb);
+};
+
+var updateActivity = function (Env, blobId, cb) {
+    var path = makeActivityPath(Env, blobId);
+    var s_data = String(+new Date());
+    Fs.writeFile(path, s_data, cb);
+};
+
+var getActivity = function (Env, blobId, cb) {
+    var path = makeActivityPath(Env, blobId);
+    Fs.readFile(path, function (err, content) {
+        if (err) { return void cb(err); }
+        try {
+            var date = new Date(+content);
+            cb(void 0, date);
+        } catch (err2) {
+            cb(err2);
+        }
+    });
+};
+
 /**********  METHODS **************/
 
 var upload = function (Env, safeKey, content, cb) {
@@ -506,6 +537,7 @@ BlobStore.create = function (config, _cb) {
         Fse.writeFile(fullPath, 'PLACEHOLDER\n', w());
     }).nThen(function () {
         var methods = {
+            BLOB_LENGTH: BLOB_LENGTH,
             isFileId: isValidId,
             status: function (safeKey, _cb) {
                 // TODO check if the final destination is a file
@@ -623,6 +655,23 @@ BlobStore.create = function (config, _cb) {
                 getUploadSize(Env, id, cb);
             },
 
+        // ACTIVITY
+            clearActivity: function (id, _cb) {
+                var cb = Util.once(Util.mkAsync(_cb));
+                if (!isValidId(id)) { return void cb("INVALID_ID"); }
+                clearActivity(Env, id, cb);
+            },
+            updateActivity: function (id, _cb) {
+                var cb = Util.once(Util.mkAsync(_cb));
+                if (!isValidId(id)) { return void cb("INVALID_ID"); }
+                updateActivity(Env, id, cb);
+            },
+            getActivity: function (id, _cb) {
+                var cb = Util.once(Util.mkAsync(_cb));
+                if (!isValidId(id)) { return void cb("INVALID_ID"); }
+                getActivity(Env, id, cb);
+            },
+
             list: {
                 blobs: function (handler, _cb) {
                     var cb = Util.once(Util.mkAsync(_cb));
diff --git a/www/common/media-tag.js b/www/common/media-tag.js
index ffc024857..e96a612c2 100644
--- a/www/common/media-tag.js
+++ b/www/common/media-tag.js
@@ -234,6 +234,22 @@ var factory = function () {
         config.Cache.setBlobCache(id, u8, cb);
     };
 
+    var headRequest = function (src, cb) {
+        var xhr = new XMLHttpRequest();
+        xhr.open("HEAD", src);
+        if (sendCredentials) { xhr.withCredentials = true; }
+        xhr.onerror = function () { return void cb("XHR_ERROR"); };
+        xhr.onreadystatechange = function() {
+            if (this.readyState === this.DONE) {
+                cb(null, Number(xhr.getResponseHeader("Content-Length")));
+            }
+        };
+        xhr.onload = function () {
+            if (/^4/.test('' + this.status)) { return void cb("XHR_ERROR " + this.status); }
+        };
+        xhr.send();
+
+    };
     var getFileSize = function (src, _cb) {
         var cb = function (e, res) {
             _cb(e, res);
@@ -243,25 +259,14 @@ var factory = function () {
         var cacheKey = getCacheKey(src);
 
         var check = function () {
-            var xhr = new XMLHttpRequest();
-            xhr.open("HEAD", src);
-            if (sendCredentials) { xhr.withCredentials = true; }
-            xhr.onerror = function () { return void cb("XHR_ERROR"); };
-            xhr.onreadystatechange = function() {
-                if (this.readyState === this.DONE) {
-                    cb(null, Number(xhr.getResponseHeader("Content-Length")));
-                }
-            };
-            xhr.onload = function () {
-                if (/^4/.test('' + this.status)) { return void cb("XHR_ERROR " + this.status); }
-            };
-            xhr.send();
+            headRequest(src, cb);
         };
 
         if (!cacheKey) { return void check(); }
 
         getBlobCache(cacheKey, function (err, u8) {
-            if (err || !u8) { return void check(); }
+            check(); // send the HEAD request to update the blob activity
+            if (err || !u8) { return; }
             cb(null, 0);
         });
     };
@@ -748,7 +753,11 @@ var factory = function () {
             });
         };
 
-        if (cfg.force) { dl(); return mediaObject; }
+        if (cfg.force) {
+            headRequest(src, function () {}); // Update activity
+            dl();
+            return mediaObject;
+        }
 
         var maxSize = typeof(config.maxDownloadSize) === "number" ? config.maxDownloadSize
                                 : (5 * 1024 * 1024);