diff --git a/snikket_web/__init__.py b/snikket_web/__init__.py
index 88860ba..b3c5015 100644
--- a/snikket_web/__init__.py
+++ b/snikket_web/__init__.py
@@ -155,6 +155,11 @@ class AppConfig:
         "sv",
     ], converter=autosplit)
     apple_store_url = environ.var("")
+    # Default limit of 1 MiB is what was discovered to be the effective limit
+    # in #67, hence we set that here for now.
+    # Future versions may change this default, and the standard deployment
+    # tools may also very well override it.
+    max_avatar_size = environ.var(1024*1024, converter=int)
 
 
 _UPPER_CASE = "".join(map(chr, range(ord("A"), ord("Z")+1)))
@@ -185,6 +190,7 @@ def create_app() -> quart.Quart:
     app.config["SITE_NAME"] = config.site_name or config.domain
     app.config["AVATAR_CACHE_TTL"] = config.avatar_cache_ttl
     app.config["APPLE_STORE_URL"] = config.apple_store_url
+    app.config["MAX_AVATAR_SIZE"] = config.max_avatar_size
 
     app.context_processor(proc)
     app.register_error_handler(
diff --git a/snikket_web/templates/unauth.html b/snikket_web/templates/unauth.html
index 897035c..10fdff3 100644
--- a/snikket_web/templates/unauth.html
+++ b/snikket_web/templates/unauth.html
@@ -9,7 +9,7 @@
 </div>
 <div id="mwrap">
 	{#- -#}
-	<div class="flashbox">
+	<div class="flashbox" id="flashbox">
 		{%- for category, message in get_flashed_messages(True) -%}
 		<div class="box {{ category }} el-5" role="alert">
 			{% if category == "success" %}
diff --git a/snikket_web/templates/user_profile.html b/snikket_web/templates/user_profile.html
index e7ce934..f420801 100644
--- a/snikket_web/templates/user_profile.html
+++ b/snikket_web/templates/user_profile.html
@@ -1,10 +1,11 @@
 {% extends "app.html" %}
-{% from "library.j2" import standard_button, form_button, avatar with context %}
+{% from "library.j2" import standard_button, form_button, render_errors, avatar with context %}
 {% block content %}
 <h1>{% trans %}Update your profile{% endtrans %}</h1>
 <div class="form layout-expanded"><form method="POST" enctype="multipart/form-data">
 	<h2 class="form-title">{% trans %}Profile{% endtrans %}</h2>
 	{{ form.csrf_token }}
+	{% call render_errors(form) %}{% endcall %}
 	<div class="f-ebox">
 		{{ form.nickname.label }}
 		{{ form.nickname(placeholder=user_info.username) }}
@@ -13,7 +14,10 @@
 		{{ form.avatar.label }}
 		<div class="avatar-wrap">
 		{%- call avatar(user_info.address, user_info.avatar_hash ) %}{% endcall -%}
-		{{ form.avatar(accept="image/png") }}
+		{{ form.avatar(accept="image/png",
+				 data_maxsize=max_avatar_size,
+				 data_warning_header=avatar_too_big_warning_header,
+				 data_maxsize_warning=avatar_too_big_warning) }}
 		</div>
 	</div>
 	<h3 class="form-title">{% trans %}Visibility{% endtrans %}</h3>
@@ -28,5 +32,38 @@
 		{%- call standard_button("back", url_for('.index'), class="secondary") %}{% trans %}Back{% endtrans %}{% endcall -%}
 		{%- call form_button("done", form.action_save, class="primary") %}{% endcall -%}
 	</div>
+	<script type="text/javascript">
+	document.getElementById("{{ form.avatar.id }}").onchange = function() {
+		var maxsize_s = this.dataset.maxsize;
+		var maxsize = parseInt(maxsize_s);
+		var existing_alert = document.getElementById("avatar-alert");
+		if (existing_alert) {
+			existing_alert.parentNode.removeChild(existing_alert);
+		}
+		if (this.files[0].size > maxsize) {
+			var warning_header = this.dataset.warningHeader;
+			var warning_text = this.dataset.maxsizeWarning;
+			var flash = document.createElement("div");
+			flash.id = "avatar-alert";
+			flash.classList.add("box");
+			flash.classList.add("alert");
+			flash.classList.add("el-5");
+			flash.setAttribute("role", "alert");
+
+			var header = document.createElement("header");
+			header.innerText = warning_header;
+			flash.appendChild(header);
+
+			var p = document.createElement("p")
+			p.innerText = warning_text + ".";
+			flash.appendChild(p);
+
+			var flashbox = document.getElementById("flashbox");
+			flashbox.appendChild(flash);
+
+			this.value = null;
+		}
+	};
+	</script>
 </form></div>
 {% endblock %}
diff --git a/snikket_web/translations/messages.pot b/snikket_web/translations/messages.pot
index 493dfe9..efa8aa1 100644
--- a/snikket_web/translations/messages.pot
+++ b/snikket_web/translations/messages.pot
@@ -8,7 +8,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: PROJECT VERSION\n"
 "Report-Msgid-Bugs-To: EMAIL@ADDRESS\n"
-"POT-Creation-Date: 2021-02-23 07:55+0100\n"
+"POT-Creation-Date: 2021-03-20 12:56+0100\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
@@ -149,39 +149,39 @@ msgstr ""
 msgid "Main"
 msgstr ""
 
-#: snikket_web/invite.py:104
+#: snikket_web/invite.py:106
 msgid "Username"
 msgstr ""
 
-#: snikket_web/invite.py:108 snikket_web/invite.py:175 snikket_web/main.py:42
+#: snikket_web/invite.py:110 snikket_web/invite.py:177 snikket_web/main.py:42
 msgid "Password"
 msgstr ""
 
-#: snikket_web/invite.py:112 snikket_web/invite.py:179
+#: snikket_web/invite.py:114 snikket_web/invite.py:181
 msgid "Confirm password"
 msgstr ""
 
-#: snikket_web/invite.py:116 snikket_web/invite.py:183
+#: snikket_web/invite.py:118 snikket_web/invite.py:185
 msgid "The passwords must match"
 msgstr ""
 
-#: snikket_web/invite.py:121
+#: snikket_web/invite.py:123
 msgid "Create account"
 msgstr ""
 
-#: snikket_web/invite.py:148
+#: snikket_web/invite.py:150
 msgid "That username is already taken"
 msgstr ""
 
-#: snikket_web/invite.py:152 snikket_web/invite.py:216
+#: snikket_web/invite.py:154 snikket_web/invite.py:218
 msgid "Registration was declined for unknown reasons"
 msgstr ""
 
-#: snikket_web/invite.py:156
+#: snikket_web/invite.py:158
 msgid "The username is not valid"
 msgstr ""
 
-#: snikket_web/invite.py:188 snikket_web/templates/user_home.html:32
+#: snikket_web/invite.py:190 snikket_web/templates/user_home.html:32
 #: snikket_web/templates/user_passwd.html:29
 msgid "Change password"
 msgstr ""
@@ -202,67 +202,77 @@ msgstr ""
 msgid "Login successful!"
 msgstr ""
 
-#: snikket_web/user.py:28
+#: snikket_web/user.py:29
 msgid "Current password"
 msgstr ""
 
-#: snikket_web/user.py:33
+#: snikket_web/user.py:34
 msgid "New password"
 msgstr ""
 
-#: snikket_web/user.py:38
+#: snikket_web/user.py:39
 msgid "Confirm new password"
 msgstr ""
 
-#: snikket_web/user.py:42
+#: snikket_web/user.py:43
 msgid "The new passwords must match"
 msgstr ""
 
-#: snikket_web/user.py:49
+#: snikket_web/user.py:50
 msgid "Sign out"
 msgstr ""
 
-#: snikket_web/user.py:54
+#: snikket_web/user.py:55
 msgid "Nobody"
 msgstr ""
 
-#: snikket_web/user.py:55
+#: snikket_web/user.py:56
 msgid "Friends only"
 msgstr ""
 
-#: snikket_web/user.py:56
+#: snikket_web/user.py:57
 msgid "Everyone"
 msgstr ""
 
 #: snikket_web/templates/admin_delete_user.html:12
-#: snikket_web/templates/admin_users.html:11 snikket_web/user.py:62
+#: snikket_web/templates/admin_users.html:11 snikket_web/user.py:63
 msgid "Display name"
 msgstr ""
 
-#: snikket_web/user.py:66
+#: snikket_web/user.py:67
 msgid "Avatar"
 msgstr ""
 
-#: snikket_web/user.py:70
+#: snikket_web/user.py:71
 msgid "Profile visibility"
 msgstr ""
 
-#: snikket_web/user.py:75
+#: snikket_web/user.py:76
 msgid "Update profile"
 msgstr ""
 
-#: snikket_web/user.py:100
+#: snikket_web/user.py:101
 msgid "Incorrect password"
 msgstr ""
 
-#: snikket_web/user.py:104
+#: snikket_web/user.py:105
 msgid "Password changed"
 msgstr ""
 
-#: snikket_web/user.py:146
+#: snikket_web/user.py:113
+msgid ""
+"The chosen avatar is too big. To be able to upload larger avatars, please"
+" use the app"
+msgstr ""
+
+#: snikket_web/user.py:161
 msgid "Profile updated"
 msgstr ""
 
+#: snikket_web/templates/unauth.html:18 snikket_web/user.py:169
+msgid "Error"
+msgstr ""
+
 #: snikket_web/templates/_footer.html:4
 #, python-format
 msgid "A <a href=\"%(about_url)s\">Snikket</a> service"
@@ -480,7 +490,7 @@ msgstr ""
 #: snikket_web/templates/admin_reset_user_password.html:25
 #: snikket_web/templates/user_logout.html:10
 #: snikket_web/templates/user_passwd.html:27
-#: snikket_web/templates/user_profile.html:28
+#: snikket_web/templates/user_profile.html:32
 msgid "Back"
 msgstr ""
 
@@ -1068,10 +1078,6 @@ msgstr ""
 msgid "Operation successful"
 msgstr ""
 
-#: snikket_web/templates/unauth.html:18
-msgid "Error"
-msgstr ""
-
 #: snikket_web/templates/user_home.html:9
 msgid "Welcome!"
 msgstr ""
@@ -1140,11 +1146,11 @@ msgstr ""
 msgid "Profile"
 msgstr ""
 
-#: snikket_web/templates/user_profile.html:19
+#: snikket_web/templates/user_profile.html:23
 msgid "Visibility"
 msgstr ""
 
-#: snikket_web/templates/user_profile.html:20
+#: snikket_web/templates/user_profile.html:24
 msgid ""
 "This section allows you to control who can see your profile information, "
 "like avatar and nickname."
diff --git a/snikket_web/user.py b/snikket_web/user.py
index 982ad7a..3f14ce6 100644
--- a/snikket_web/user.py
+++ b/snikket_web/user.py
@@ -9,6 +9,7 @@ from quart import (
     redirect,
     url_for,
     flash,
+    current_app,
 )
 import quart.exceptions
 
@@ -109,9 +110,17 @@ async def change_pw() -> typing.Union[str, quart.Response]:
     return await render_template("user_passwd.html", form=form)
 
 
+EAVATARTOOBIG = _l(
+    "The chosen avatar is too big. To be able to upload larger "
+    "avatars, please use the app"
+)
+
+
 @bp.route("/profile", methods=["GET", "POST"])
 @client.require_session()
 async def profile() -> typing.Union[str, quart.Response]:
+    max_avatar_size = current_app.config["MAX_AVATAR_SIZE"]
+
     form = ProfileForm()
     if request.method != "POST":
         user_info = await client.get_user_info()
@@ -125,30 +134,40 @@ async def profile() -> typing.Union[str, quart.Response]:
     if form.validate_on_submit():
         user_info = await client.get_user_info()
 
+        ok = True
         file_info = (await request.files).get(form.avatar.name)
         if file_info is not None:
             mimetype = file_info.mimetype
             data = file_info.stream.read()
-            if len(data) > 0:
+            if len(data) > max_avatar_size:
+                print(len(data), max_avatar_size)
+                form.avatar.errors.append(EAVATARTOOBIG)
+                ok = False
+            elif len(data) > 0:
                 await client.set_user_avatar(data, mimetype)
 
-        if user_info.get("nickname") != form.nickname.data:
-            await client.set_user_nickname(form.nickname.data)
+        if ok:
+            if user_info.get("nickname") != form.nickname.data:
+                await client.set_user_nickname(form.nickname.data)
 
-        access_model = form.profile_access_model.data
-        await asyncio.gather(
-            client.set_avatar_access_model(access_model),
-            client.set_vcard_access_model(access_model),
-            client.set_nickname_access_model(access_model),
-        )
+            access_model = form.profile_access_model.data
+            await asyncio.gather(
+                client.set_avatar_access_model(access_model),
+                client.set_vcard_access_model(access_model),
+                client.set_nickname_access_model(access_model),
+            )
 
-        await flash(
-            _("Profile updated"),
-            "success",
-        )
-        return redirect(url_for(".profile"))
+            await flash(
+                _("Profile updated"),
+                "success",
+            )
+            return redirect(url_for(".profile"))
 
-    return await render_template("user_profile.html", form=form)
+    return await render_template("user_profile.html",
+                                 form=form,
+                                 max_avatar_size=max_avatar_size,
+                                 avatar_too_big_warning_header=_l("Error"),
+                                 avatar_too_big_warning=EAVATARTOOBIG)
 
 
 @bp.route("/logout", methods=["GET", "POST"])