diff --git a/bookwyrm/static/js/autocomplete.js b/bookwyrm/static/js/autocomplete.js
new file mode 100644
index 000000000..0ba3e2172
--- /dev/null
+++ b/bookwyrm/static/js/autocomplete.js
@@ -0,0 +1,164 @@
+(function () {
+    "use strict";
+
+    /**
+     * Suggest a completion as a user types
+     *
+     * Use `data-autocomplete="<completions set identifier>"`on the input field.
+     * specifying the trie to be used for autocomplete
+     *
+     * @example
+     * <input
+     *     type="input"
+     *     data-autocomplete="mimetype"
+     * >
+     * @param  {Event} event
+     * @return {undefined}
+     */
+    function autocomplete(event) {
+        const input = event.target;
+
+        // Get suggestions
+        let trie = tries[input.getAttribute("data-autocomplete")];
+
+        let suggestions = getSuggestions(input.value, trie);
+
+        const boxId = input.getAttribute("list");
+
+        // Create suggestion box, if needed
+        let suggestionsBox = document.getElementById(boxId);
+
+        // Clear existing suggestions
+        suggestionsBox.innerHTML = "";
+
+        // Populate suggestions box
+        suggestions.forEach((suggestion) => {
+            const suggestionItem = document.createElement("option");
+
+            suggestionItem.textContent = suggestion;
+            suggestionsBox.appendChild(suggestionItem);
+        });
+    }
+
+    function getSuggestions(input, trie) {
+        // Follow the trie through the provided input
+        input.split("").forEach((letter) => {
+            if (!trie) {
+                return;
+            }
+
+            trie = trie[letter];
+        });
+
+        if (!trie) {
+            return [];
+        }
+
+        return searchTrie(trie);
+    }
+
+    function searchTrie(trie) {
+        const options = Object.values(trie);
+
+        if (typeof trie == "string") {
+            return [trie];
+        }
+
+        return options
+            .map((option) => {
+                const newTrie = option;
+
+                if (typeof newTrie == "string") {
+                    return [newTrie];
+                }
+
+                return searchTrie(newTrie);
+            })
+            .reduce((prev, next) => prev.concat(next));
+    }
+
+    document.querySelectorAll("[data-autocomplete]").forEach((input) => {
+        input.addEventListener("input", autocomplete);
+    });
+})();
+
+const tries = {"mimetype": {
+        a: {
+            a: {
+                c: "AAC",
+            },
+            z: {
+                w: "AZW",
+            },
+        },
+        d: {
+            a: {
+                i: {
+                    s: {
+                        y: "Daisy",
+                    },
+                },
+            },
+        },
+        e: {
+            p: {
+                u: {
+                    b: "ePub",
+                },
+            },
+        },
+        f: {
+            l: {
+                a: {
+                    c: "FLAC",
+                },
+            },
+        },
+        h: {
+            t: {
+                m: {
+                    l: "HTML",
+                },
+            },
+        },
+        m: {
+            4: {
+                a: "M4A",
+                b: "M4B",
+            },
+            o: {
+                b: {
+                    i: "MOBI",
+                },
+            },
+            p: {
+                3: "MP3",
+            },
+        },
+        o: {
+            g: {
+                g: "OGG",
+            },
+        },
+        p: {
+            d: {
+                f: "PDF",
+            },
+            l: {
+                a: {
+                    i: {
+                        n: {
+                            t: {
+                                e: {
+                                    x: {
+                                        t: "Plaintext",
+                                    },
+                                },
+                            },
+                        },
+                    },
+                },
+            },
+        },
+    },
+};
diff --git a/bookwyrm/templates/book/book.html b/bookwyrm/templates/book/book.html
index c8c78e0e9..f6d9929dd 100644
--- a/bookwyrm/templates/book/book.html
+++ b/bookwyrm/templates/book/book.html
@@ -386,4 +386,5 @@
 
 {% block scripts %}
 <script src="{% static "js/vendor/tabs.js" %}?v={{ js_cache }}"></script>
+<script src="{% static "js/autocomplete.js" %}?v={{ js_cache }}"></script>
 {% endblock %}
diff --git a/bookwyrm/templates/book/file_links/add_link_modal.html b/bookwyrm/templates/book/file_links/add_link_modal.html
index fc8b90597..dfc222ee9 100644
--- a/bookwyrm/templates/book/file_links/add_link_modal.html
+++ b/bookwyrm/templates/book/file_links/add_link_modal.html
@@ -1,5 +1,6 @@
 {% extends 'components/modal.html' %}
 {% load i18n %}
+{% load static %}
 
 {% block modal-title %}
 {% trans "Add file link" %}
@@ -26,7 +27,19 @@
     </div>
     <div class="column is-one-fifth">
         <label class="label" for="id_filetype">{% trans "File type:" %}</label>
-        <input type="text" name="filetype" maxlength="5" class="input" required="" id="id_filetype" value="{% firstof file_link_form.filetype.value "" %}" placeholder="PDF">
+        <input
+            type="text"
+            name="filetype"
+            maxlength="5"
+            class="input"
+            required=""
+            id="id_filetype"
+            value="{% firstof file_link_form.filetype.value '' %}"
+            placeholder="ePub"
+            list="mimetypes-list"
+            data-autocomplete="mimetype"
+        >
+        <datalist id="mimetypes-list"></datalist>
         {% include 'snippets/form_errors.html' with errors_list=file_link_form.filetype.errors id="desc_filetype" %}
     </div>
 </div>
diff --git a/bookwyrm/templates/book/file_links/file_link_page.html b/bookwyrm/templates/book/file_links/file_link_page.html
index 902057af2..00efe5089 100644
--- a/bookwyrm/templates/book/file_links/file_link_page.html
+++ b/bookwyrm/templates/book/file_links/file_link_page.html
@@ -1,5 +1,6 @@
 {% extends 'layout.html' %}
 {% load i18n %}
+{% load static %}
 
 {% block title %}
 {% trans "File Links" %}
@@ -8,3 +9,7 @@
 {% block content %}
 {% include "book/file_links/add_link_modal.html" with book=book active=True static=True id="file-link" %}
 {% endblock %}
+
+{% block scripts %}
+<script src="{% static "js/autocomplete.js" %}?v={{ js_cache }}"></script>
+{% endblock %}