diff --git a/README.md b/README.md
index 1c34c55..f7d4fe0 100644
--- a/README.md
+++ b/README.md
@@ -18,6 +18,7 @@
     - [debian-cd](#debian-cd)
     - [docker-ce](#docker-ce)
     - [fedora](#fedora)
+    - [flatpak](#flatpak)
     - [freebsd-pkg](#freebsd-pkg)
     - [freebsd-ports](#freebsd-ports)
     - [ghcup](#ghcup)
@@ -193,6 +194,17 @@ See [dist conf](https://pagure.io/quick-fedora-mirror/blob/master/f/quick-fedora
 
 Note: This image is not in use now, as `quick-fedora-mirror` has some mysterious bugs when being used.
 
+### flatpak
+
+[![flatpak](https://img.shields.io/docker/image-size/ustcmirror/flatpak/latest)](https://hub.docker.com/r/ustcmirror/flatpak "flatpak")
+[![flatpak](https://img.shields.io/docker/pulls/ustcmirror/flatpak)](https://hub.docker.com/r/ustcmirror/flatpak "flatpak")
+
+A simple sync script to sync necessary metadata for flatpak. **This DOES NOT SYNC ANY BLOB FILES.**
+
+| Parameter    | Description      |
+| ------------ | ---------------- |
+| `USER_AGENT` | user agent used  |
+
 ### freebsd-pkg
 
 [![freebsd-pkg](https://img.shields.io/docker/image-size/ustcmirror/freebsd-pkg/latest)](https://hub.docker.com/r/ustcmirror/freebsd-pkg "freebsd-pkg")
diff --git a/flatpak/.gitignore b/flatpak/.gitignore
new file mode 100644
index 0000000..63e6e61
--- /dev/null
+++ b/flatpak/.gitignore
@@ -0,0 +1,3 @@
+summary.idx*
+summaries/
+config
diff --git a/flatpak/Dockerfile b/flatpak/Dockerfile
new file mode 100644
index 0000000..82bcb6a
--- /dev/null
+++ b/flatpak/Dockerfile
@@ -0,0 +1,10 @@
+FROM ustcmirror/base:alpine
+LABEL maintainer="Keyu Tao <taoky AT ustclug.org>"
+
+RUN <<EOF
+    set -euo pipefail
+    apk add --no-cache python3 py3-gobject3 py3-requests
+EOF
+
+ADD sync.sh /
+ADD sync.py /
diff --git a/flatpak/sync.py b/flatpak/sync.py
new file mode 100644
index 0000000..5d95d76
--- /dev/null
+++ b/flatpak/sync.py
@@ -0,0 +1,122 @@
+#!/usr/bin/python3
+from gi.repository import GLib
+import requests
+import hashlib
+import os
+from email.utils import formatdate, parsedate_to_datetime
+from contextlib import contextmanager
+
+# https://github.com/flatpak/flatpak/blob/7a6c98c563a43a0d4b601b6bc7daaff3e4776efb/doc/flatpak-summaries.txt
+SUMMARY_VARIANT = GLib.VariantType("(a{s(ayaaya{sv})}a{sv})")
+FLATHUB = "https://dl.flathub.org/repo/"
+
+USER_AGENT = os.getenv(
+    "USER_AGENT", "flatpak-sync (+https://github.com/ustclug/ustcmirror-images)"
+)
+requests.utils.default_user_agent = lambda: USER_AGENT
+TIMEOUT_OPTION = (7, 30)
+
+
+def set_retry(max_retries):
+    def decorate(func):
+        def wrapper(self, *args, **kwargs):
+            func(self, *args, **kwargs)
+            self.max_retries = max_retries
+
+        return wrapper
+
+    return decorate
+
+
+func = requests.adapters.HTTPAdapter.__init__
+requests.adapters.HTTPAdapter.__init__ = set_retry(3)(func)
+
+
+@contextmanager
+def overwrite(file_path, mode: str = "w", tmp_suffix: str = ".tmp"):
+    tmp_path = file_path + tmp_suffix
+    try:
+        with open(tmp_path, mode) as tmp_file:
+            yield tmp_file
+        os.rename(tmp_path, file_path)
+    except Exception:
+        # well, just keep the tmp_path in error case.
+        raise
+
+
+def download_if_modified(url, local_path, check_path=None):
+    headers = {}
+    if check_path:
+        local_check_path = check_path
+    else:
+        local_check_path = local_path
+    if os.path.exists(local_check_path):
+        mtime = os.path.getmtime(local_check_path)
+        headers["If-Modified-Since"] = formatdate(mtime, usegmt=True)
+    response = requests.get(url, headers=headers, stream=True, timeout=TIMEOUT_OPTION)
+    response.raise_for_status()
+    if response.status_code == 200:
+        print("Downloading", url)
+        with overwrite(local_path, "wb") as f:
+            for chunk in response.iter_content(chunk_size=8192):
+                f.write(chunk)
+        if "Last-Modified" in response.headers:
+            mtime = parsedate_to_datetime(response.headers["Last-Modified"])
+            os.utime(local_path, (mtime.timestamp(), mtime.timestamp()))
+    return response
+
+
+def main():
+    download_if_modified(FLATHUB + "config", "config")
+    # download summary.idx
+    url = FLATHUB + "summary.idx"
+    resp = download_if_modified(url, "summary.idx.bak", "summary.idx")
+    if resp.status_code == 304:
+        # nothing to do, bye~
+        exit(0)
+    with open("summary.idx.bak", "rb") as f:
+        summary_data = f.read()
+
+    # parse summary.idx
+    summary = GLib.Variant.new_from_bytes(
+        SUMMARY_VARIANT, GLib.Bytes.new(summary_data), False
+    )
+    summary_sha256 = hashlib.sha256(summary_data).digest()
+    os.makedirs("summaries", exist_ok=True)
+
+    sha256_filepath = f"summaries/{summary_sha256.hex()}.idx.sig"
+    download_if_modified(FLATHUB + sha256_filepath, sha256_filepath)
+
+    # get all subsummary digests
+    subsummaries = summary[0]
+    all_digests = []
+
+    for subsummary_name, subsummary_info in subsummaries.items():
+        current_digest = subsummary_info[0]
+        previous_digests = subsummary_info[1]
+
+        all_digests.append(current_digest)
+        all_digests.extend(previous_digests)
+
+    all_digests = ["".join(f"{y:02x}" for y in x) for x in all_digests]
+    for i in all_digests:
+        filepath = f"summaries/{i}.gz"
+        download_if_modified(FLATHUB + filepath, filepath)
+
+    os.rename("summary.idx.bak", "summary.idx")
+
+    # Remove old summaries
+    for filename in os.listdir("summaries"):
+        if filename.endswith(".sig"):
+            if filename != f"{summary_sha256.hex()}.idx.sig":
+                print("Removing", filename)
+                os.remove(f"summaries/{filename}")
+        elif filename.endswith(".gz"):
+            digest = filename[:-3]
+            if digest not in all_digests:
+                print("Removing", filename)
+                os.remove(f"summaries/{filename}")
+
+
+if __name__ == "__main__":
+    main()
diff --git a/flatpak/sync.sh b/flatpak/sync.sh
new file mode 100755
index 0000000..dcaa305
--- /dev/null
+++ b/flatpak/sync.sh
@@ -0,0 +1,4 @@
+#!/bin/bash
+
+cd "$TO"
+exec python3 /sync.py