diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 0000000..cbc04c9
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,22 @@
+# Changelog
+
+## [Unreleased]
+
+### Added
+- Firefox support
+
+### Changed
+- explicit close of databases
+- Updated readme
+- Add changelog
+
+## [0.1.0] - 2024-06-07
+
+### Added
+- initial release
+- `init` subcommand
+- `add` subcommand
+- Chromium support
+
+[unreleased]: https://github.com/qwjyh/browser-history-merger/compare/v0.1.0...HEAD
+[0.1.0]: https://github.com/qwjyh/browser-history-merger/releases/tag/v0.1.0
diff --git a/README.md b/README.md
index 702892c..adf0461 100644
--- a/README.md
+++ b/README.md
@@ -2,20 +2,32 @@
 
 Merge browser histories into a single database.
 
-# Usage
-## Initialization
+## Usage
+### Initialization
 For the first execution on each device and browser, do
 ```sh
 browser-history-merger path/to/merged.db init browser-id path/to/browser/history/database
 ```
 `browser-id` should be unique to identify browser and machine.
 
-## Add histories
+### Add histories
 Then add histories to the database by
 ```sh
 browser-history-merger path/to/merged.db add browser-id
 ```
 
-# Tips
+## Supported environments
+Python 3.12 (works with standard libraries only)
+
+- Chromium
+  - Tested:
+    - chrome on windows, linux
+    - brave on windows, linux
+    - vivaldi on linux
+- Firefox
+  - Tested:
+    - firefox on windows
+
+## Tips
 The program is a single file `./src/browser_history_merger/__init__.py` and can be used as a script.