diff --git a/tildes/scss/modules/_toast.scss b/tildes/scss/modules/_toast.scss
index 2a7aaea..49119ed 100644
--- a/tildes/scss/modules/_toast.scss
+++ b/tildes/scss/modules/_toast.scss
@@ -2,8 +2,14 @@
 // SPDX-License-Identifier: AGPL-3.0-or-later
 
 .toast {
+  @extend %text-container;
+
   margin: 1rem 0;
   font-weight: bold;
+
+  ul {
+    margin-bottom: 1rem;
+  }
 }
 
 .toast-minor {
diff --git a/tildes/static/js/behaviors/autocomplete-input.js b/tildes/static/js/behaviors/autocomplete-input.js
index 910094d..340e349 100644
--- a/tildes/static/js/behaviors/autocomplete-input.js
+++ b/tildes/static/js/behaviors/autocomplete-input.js
@@ -70,6 +70,7 @@ $.onmount("[data-js-autocomplete-input]", function() {
                 for (var i = 0; i < dataPieces.length; i++) {
                     if (dataPieces[i].indexOf("tags=") === 0) {
                         dataPieces[i] += $autocompleteInput.val();
+                        $autocompleteInput.val("");
                         break;
                     }
                 }
diff --git a/tildes/tildes/templates/includes/new_topic_form.jinja2 b/tildes/tildes/templates/includes/new_topic_form.jinja2
new file mode 100644
index 0000000..d139bdc
--- /dev/null
+++ b/tildes/tildes/templates/includes/new_topic_form.jinja2
@@ -0,0 +1,79 @@
+{# Copyright (c) 2019 Tildes contributors <code@tildes.net> #}
+{# SPDX-License-Identifier: AGPL-3.0-or-later #}
+
+{% from "macros/datetime.jinja2" import adaptive_date_responsive %}
+{% from 'macros/forms.jinja2' import markdown_textarea, topic_tagging %}
+
+<form
+  id="new-topic"
+  method="post"
+  autocomplete="off"
+  action="/~{{ group.path }}/topics"
+  data-ic-post-to="/~{{ group.path }}/topics"
+  data-js-prevent-double-submit
+  data-js-confirm-leave-page-unsaved
+>
+  <input type="hidden" name="csrf_token" value="{{ get_csrf_token() }}">
+
+  <div class="toast toast-minor">
+    <h2>Tildes prioritizes high-quality content and discussions</h2>
+    <p>Please post topics that are interesting, informative, or have the potential to start a good discussion.</p>
+    <p>Please <em>avoid</em> posting topics that are primarily for entertainment or that don't have discussion value.</p>
+  </div>
+
+  <div class="form-group">
+    <label class="form-label" for="title">Title</label>
+    <input class="form-input" id="title" name="title" type="text" placeholder="Title" required data-js-auto-focus
+      {% if title %}value="{{ title }}"{% endif %}
+    >
+  </div>
+
+  <fieldset>
+    <legend>Enter a link, text, or both:</legend>
+    <div class="form-group">
+      <label class="form-label" for="link">Link</label>
+      <input class="form-input" id="link" name="link" type="URL" placeholder="Link"
+        {% if link %}value="{{ link }}"{% endif %}
+      >
+      <p class="form-input-note">If you enter a link, your post will be a link topic (whether you also include text or not).</p>
+    </div>
+
+    <div class="form-group">
+      {{ markdown_textarea(text=markdown) }}
+      <p class="form-input-note">If you enter only text (and no link), your post will be a text topic.</p>
+      <p class="form-input-note">If you also enter a link, this text will be posted as the first comment and can be used to add more information or give your thoughts on the linked content. Adding text when posting a link is not required, but it can help get the discussion started.</p>
+      </p>
+    </div>
+  </fieldset>
+
+  {{ topic_tagging(autocomplete_options=group.common_topic_tags, value=tags) }}
+
+  <div class="form-buttons">
+    <button type="submit" class="btn btn-primary">Post topic</button>
+    {% if previous_topics %}
+      <div class="form-status form-status-error">Link has been posted before, see below</div>
+    {% endif %}
+  </div>
+
+  {% if previous_topics %}
+    <div class="toast toast-minor toast-warning">
+      <h2>This link has been posted previously:</h2>
+
+      <ul>
+      {% for previous_topic in previous_topics %}
+        <li>{{ adaptive_date_responsive(previous_topic.created_time) }} in ~{{ previous_topic.group }}: <a href="{{ previous_topic.permalink }}" target="_blank">{{ previous_topic.title }}</a></li>
+      {% endfor %}
+      </ul>
+
+      <p>If you want to post it again anyway, check the box below and click the "Post topic" button above again.</p>
+
+      <div class="form-group ml-2">
+        <label class="form-checkbox">
+          <input type="checkbox" id="confirm_repost" name="confirm_repost" value="true">
+          <i class="form-icon"></i> Re-post this link in ~{{ group }}
+        </label>
+      </div>
+    </div>
+  {% endif %}
+</form>
+
diff --git a/tildes/tildes/templates/new_topic.jinja2 b/tildes/tildes/templates/new_topic.jinja2
index e220d20..0807a51 100644
--- a/tildes/tildes/templates/new_topic.jinja2
+++ b/tildes/tildes/templates/new_topic.jinja2
@@ -3,8 +3,6 @@
 
 {% extends 'base_no_sidebar.jinja2' %}
 
-{% from 'macros/forms.jinja2' import markdown_textarea, topic_tagging %}
-
 {% block title %}New topic{% endblock %}
 
 {% block header_context_link %}
@@ -14,48 +12,5 @@
 {% block main_heading %}Post a new topic in ~{{ group.path }}{% endblock %}
 
 {% block content %}
-  <form
-    id="new-topic"
-    method="post"
-    autocomplete="off"
-    action="/~{{ group.path }}/topics"
-    data-ic-post-to="/~{{ group.path }}/topics"
-    data-js-prevent-double-submit
-    data-js-confirm-leave-page-unsaved
-  >
-    <input type="hidden" name="csrf_token" value="{{ get_csrf_token() }}">
-
-    <div class="toast toast-minor">
-      <h2>Tildes prioritizes high-quality content and discussions</h2>
-      <p>Please post topics that are interesting, informative, or have the potential to start a good discussion.</p>
-      <p>Please <em>avoid</em> posting topics that are primarily for entertainment or that don't have discussion value.</p>
-    </div>
-
-    <div class="form-group">
-      <label class="form-label" for="title">Title</label>
-      <input class="form-input" id="title" name="title" type="text" placeholder="Title" required data-js-auto-focus>
-    </div>
-
-    <fieldset>
-      <legend>Enter a link, text, or both:</legend>
-      <div class="form-group">
-        <label class="form-label" for="link">Link</label>
-        <input class="form-input" id="link" name="link" type="URL" placeholder="Link">
-        <p class="form-input-note">If you enter a link, your post will be a link topic (whether you also include text or not).</p>
-      </div>
-
-      <div class="form-group">
-        {{ markdown_textarea() }}
-        <p class="form-input-note">If you enter only text (and no link), your post will be a text topic.</p>
-        <p class="form-input-note">If you also enter a link, this text will be posted as the first comment and can be used to add more information or give your thoughts on the linked content. Adding text when posting a link is not required, but it can help get the discussion started.</p>
-        </p>
-      </div>
-    </fieldset>
-
-    {{ topic_tagging(autocomplete_options=group.common_topic_tags) }}
-
-    <div class="form-buttons">
-      <button type="submit" class="btn btn-primary">Post topic</button>
-    </div>
-  </form>
+  {% include "includes/new_topic_form.jinja2" %}
 {% endblock %}
diff --git a/tildes/tildes/views/topic.py b/tildes/tildes/views/topic.py
index a3e1ad4..346b1cc 100644
--- a/tildes/tildes/views/topic.py
+++ b/tildes/tildes/views/topic.py
@@ -4,12 +4,14 @@
 """Views related to posting/viewing topics and comments on them."""
 
 from collections import namedtuple
-from typing import Any, Optional
+from typing import Any, Optional, Union
 
 from marshmallow import missing, ValidationError
-from marshmallow.fields import String
+from marshmallow.fields import Boolean, String
 from pyramid.httpexceptions import HTTPFound
+from pyramid.renderers import render_to_response
 from pyramid.request import Request
+from pyramid.response import Response
 from pyramid.view import view_config
 from sqlalchemy import cast
 from sqlalchemy.sql.expression import any_, desc
@@ -43,14 +45,50 @@ DefaultSettings = namedtuple("DefaultSettings", ["order", "period"])
 
 @view_config(route_name="group_topics", request_method="POST", permission="post_topic")
 @use_kwargs(TopicSchema(only=("title", "markdown", "link")))
-@use_kwargs({"tags": String(missing="")})
+@use_kwargs({"tags": String(missing=""), "confirm_repost": Boolean(missing=False)})
 def post_group_topics(
-    request: Request, title: str, markdown: str, link: str, tags: str
-) -> HTTPFound:
+    request: Request,
+    title: str,
+    markdown: str,
+    link: str,
+    tags: str,
+    confirm_repost: bool,
+) -> Union[HTTPFound, Response]:
     """Post a new topic to a group."""
+    # pylint: disable=too-many-arguments
     group = request.context
 
     if link:
+        # check to see if this link has been posted before
+        previous_topics = (
+            request.db_session.query(Topic)
+            .filter(Topic.link == link)
+            .order_by(desc(Topic.created_time))
+            .limit(5)
+            .all()
+        )
+
+        if previous_topics and not confirm_repost:
+            # Render partial form for Intercooler.js request, whole page for normal POST
+            # (I don't like this much, there must be a better way to handle this)
+            if "X-IC-Request" in request.headers:
+                template = "tildes:templates/includes/new_topic_form.jinja2"
+            else:
+                template = "tildes:templates/new_topic.jinja2"
+
+            return render_to_response(
+                template,
+                {
+                    "group": group,
+                    "title": title,
+                    "link": link,
+                    "markdown": markdown,
+                    "tags": tags,
+                    "previous_topics": previous_topics,
+                },
+                request=request,
+            )
+
         new_topic = Topic.create_link_topic(
             group=group, author=request.user, title=title, link=link
         )