diff --git a/src/browser/env.zig b/src/browser/env.zig
index 8d3e253b..957577ea 100644
--- a/src/browser/env.zig
+++ b/src/browser/env.zig
@@ -35,6 +35,7 @@ const WebApis = struct {
         @import("storage/storage.zig").Interfaces,
         @import("url/url.zig").Interfaces,
         @import("xhr/xhr.zig").Interfaces,
+        @import("url/form_data.zig").Interfaces,
         @import("xmlserializer/xmlserializer.zig").Interfaces,
     });
 };
diff --git a/src/browser/url/form_data.zig b/src/browser/url/form_data.zig
new file mode 100644
index 00000000..192bfacb
--- /dev/null
+++ b/src/browser/url/form_data.zig
@@ -0,0 +1,245 @@
+// Copyright (C) 2023-2024  Lightpanda (Selecy SAS)
+//
+// Francis Bouvier <francis@lightpanda.io>
+// Pierre Tachoire <pierre@lightpanda.io>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as
+// published by the Free Software Foundation, either version 3 of the
+// License, or (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+const std = @import("std");
+
+const Allocator = std.mem.Allocator;
+
+const iterator = @import("../iterator/iterator.zig");
+const SessionState = @import("../env.zig").SessionState;
+
+pub const Interfaces = .{
+    FormData,
+    KeyIterable,
+    ValueIterable,
+    EntryIterable,
+};
+
+// We store the values in an ArrayList rather than a an
+// StringArrayHashMap([]const u8)  because of the way the iterators (i.e., keys(),
+// values() and entries()) work. The FormData can contain duplicate keys, and
+// each iteration yields 1 key=>value pair. So, given:
+//
+//  let f = new FormData();
+//  f.append('a', '1');
+//  f.append('a', '2');
+//
+// Then we'd expect f.keys(), f.values() and f.entries() to yield 2 results:
+//  ['a', '1']
+//  ['a', '2']
+//
+// This is much easier to do with an ArrayList than a HashMap, especially given
+// that the FormData could be mutated while iterating.
+// The downside is that most of the normal operations are O(N).
+pub const FormData = struct {
+    entries: std.ArrayListUnmanaged(Entry),
+
+    pub fn constructor() FormData {
+        return .{
+            .entries = .empty,
+        };
+    }
+
+    pub fn _get(self: *const FormData, key: []const u8) ?[]const u8 {
+        const result = self.find(key) orelse return null;
+        return result.entry.value;
+    }
+
+    pub fn _getAll(self: *const FormData, key: []const u8, state: *SessionState) ![][]const u8 {
+        const arena = state.call_arena;
+        var arr: std.ArrayListUnmanaged([]const u8) = .empty;
+        for (self.entries.items) |entry| {
+            if (std.mem.eql(u8, key, entry.key)) {
+                try arr.append(arena, entry.value);
+            }
+        }
+        return arr.items;
+    }
+
+    pub fn _has(self: *const FormData, key: []const u8) bool {
+        return self.find(key) != null;
+    }
+
+    // TODO: value should be a string or blog
+    // TODO: another optional parameter for the filename
+    pub fn _set(self: *FormData, key: []const u8, value: []const u8, state: *SessionState) !void {
+        self._delete(key);
+        return self._append(key, value, state);
+    }
+
+    // TODO: value should be a string or blog
+    // TODO: another optional parameter for the filename
+    pub fn _append(self: *FormData, key: []const u8, value: []const u8, state: *SessionState) !void {
+        const arena = state.arena;
+        return self.entries.append(arena, .{ .key = try arena.dupe(u8, key), .value = try arena.dupe(u8, value) });
+    }
+
+    pub fn _delete(self: *FormData, key: []const u8) void {
+        var i: usize = 0;
+        while (i < self.entries.items.len) {
+            const entry = self.entries.items[i];
+            if (std.mem.eql(u8, key, entry.key)) {
+                _ = self.entries.swapRemove(i);
+            } else {
+                i += 1;
+            }
+        }
+    }
+
+    pub fn _keys(self: *const FormData) KeyIterable {
+        return .{ .inner = .{ .entries = &self.entries } };
+    }
+
+    pub fn _values(self: *const FormData) ValueIterable {
+        return .{ .inner = .{ .entries = &self.entries } };
+    }
+
+    pub fn _entries(self: *const FormData) EntryIterable {
+        return .{ .inner = .{ .entries = &self.entries } };
+    }
+
+    pub fn _symbol_iterator(self: *const FormData) EntryIterable {
+        return self._entries();
+    }
+
+    const FindResult = struct {
+        index: usize,
+        entry: Entry,
+    };
+
+    fn find(self: *const FormData, key: []const u8) ?FindResult {
+        for (self.entries.items, 0..) |entry, i| {
+            if (std.mem.eql(u8, key, entry.key)) {
+                return .{ .index = i, .entry = entry };
+            }
+        }
+        return null;
+    }
+};
+
+const Entry = struct {
+    key: []const u8,
+    value: []const u8,
+};
+
+const KeyIterable = iterator.Iterable(KeyIterator, "FormDataKeyIterator");
+const ValueIterable = iterator.Iterable(ValueIterator, "FormDataValueIterator");
+const EntryIterable = iterator.Iterable(EntryIterator, "FormDataEntryIterator");
+
+const KeyIterator = struct {
+    index: usize = 0,
+    entries: *const std.ArrayListUnmanaged(Entry),
+
+    pub fn _next(self: *KeyIterator) ?[]const u8 {
+        const index = self.index;
+        if (index == self.entries.items.len) {
+            return null;
+        }
+        self.index += 1;
+        return self.entries.items[index].key;
+    }
+};
+
+const ValueIterator = struct {
+    index: usize = 0,
+    entries: *const std.ArrayListUnmanaged(Entry),
+
+    pub fn _next(self: *ValueIterator) ?[]const u8 {
+        const index = self.index;
+        if (index == self.entries.items.len) {
+            return null;
+        }
+        self.index += 1;
+        return self.entries.items[index].value;
+    }
+};
+
+const EntryIterator = struct {
+    index: usize = 0,
+    entries: *const std.ArrayListUnmanaged(Entry),
+
+    pub fn _next(self: *EntryIterator) ?struct { []const u8, []const u8 } {
+        const index = self.index;
+        if (index == self.entries.items.len) {
+            return null;
+        }
+        self.index += 1;
+        const entry = self.entries.items[index];
+        return .{ entry.key, entry.value };
+    }
+};
+
+const testing = @import("../../testing.zig");
+test "FormData" {
+    var runner = try testing.jsRunner(testing.tracking_allocator, .{});
+    defer runner.deinit();
+
+    try runner.testCases(&.{
+        .{ "let f = new FormData()", null },
+        .{ "f.get('a')", "null" },
+        .{ "f.has('a')", "false" },
+        .{ "f.getAll('a')", "" },
+        .{ "f.delete('a')", "undefined" },
+
+        .{ "f.set('a', 1)", "undefined" },
+        .{ "f.has('a')", "true" },
+        .{ "f.get('a')", "1" },
+        .{ "f.getAll('a')", "1" },
+
+        .{ "f.append('a', 2)", "undefined" },
+        .{ "f.has('a')", "true" },
+        .{ "f.get('a')", "1" },
+        .{ "f.getAll('a')", "1,2" },
+
+        .{ "f.append('b', '3')", "undefined" },
+        .{ "f.has('a')", "true" },
+        .{ "f.get('a')", "1" },
+        .{ "f.getAll('a')", "1,2" },
+        .{ "f.has('b')", "true" },
+        .{ "f.get('b')", "3" },
+        .{ "f.getAll('b')", "3" },
+
+        .{ "let acc = [];", null },
+        .{ "for (const key of f.keys()) { acc.push(key) }; acc;", "a,a,b" },
+
+        .{ "acc = [];", null },
+        .{ "for (const value of f.values()) { acc.push(value) }; acc;", "1,2,3" },
+
+        .{ "acc = [];", null },
+        .{ "for (const entry of f.entries()) { acc.push(entry) }; acc;", "a,1,a,2,b,3" },
+
+        .{ "acc = [];", null },
+        .{ "for (const entry of f) { acc.push(entry) }; acc;", "a,1,a,2,b,3" },
+
+        .{ "f.delete('a')", "undefined" },
+        .{ "f.has('a')", "false" },
+        .{ "f.has('b')", "true" },
+
+        .{ "acc = [];", null },
+        .{ "for (const key of f.keys()) { acc.push(key) }; acc;", "b" },
+
+        .{ "acc = [];", null },
+        .{ "for (const value of f.values()) { acc.push(value) }; acc;", "3" },
+
+        .{ "acc = [];", null },
+        .{ "for (const entry of f.entries()) { acc.push(entry) }; acc;", "b,3" },
+
+        .{ "acc = [];", null },
+        .{ "for (const entry of f) { acc.push(entry) }; acc;", "b,3" },
+    }, .{});
+}