Update README.md to enhance TLS backend documentation and clarify platform-specific certificate handling

README.md

@@ -64,26 +64,14 @@ if (auto res = cli.Get("/hi")) {
 
 cpp-httplib supports multiple TLS backends through an abstraction layer:
 
-| Backend | Define | Libraries |
-| :------ | :----- | :-------- |
-| OpenSSL | `CPPHTTPLIB_OPENSSL_SUPPORT` | `libssl`, `libcrypto` |
-| Mbed TLS | `CPPHTTPLIB_MBEDTLS_SUPPORT` | `libmbedtls`, `libmbedx509`, `libmbedcrypto` |
-| wolfSSL | `CPPHTTPLIB_WOLFSSL_SUPPORT` | `libwolfssl` |
+| Backend | Define | Libraries | Notes |
+| :------ | :----- | :-------- | :---- |
+| OpenSSL | `CPPHTTPLIB_OPENSSL_SUPPORT` | `libssl`, `libcrypto` | [3.0 or later](https://www.openssl.org/policies/releasestrat.html) required |
+| Mbed TLS | `CPPHTTPLIB_MBEDTLS_SUPPORT` | `libmbedtls`, `libmbedx509`, `libmbedcrypto` | 2.x and 3.x supported (auto-detected) |
+| wolfSSL | `CPPHTTPLIB_WOLFSSL_SUPPORT` | `libwolfssl` | 5.x supported; must build with `--enable-opensslall` |
 
 > [!NOTE]
-> OpenSSL 3.0 or later is required. Please see [this page](https://www.openssl.org/policies/releasestrat.html) for more information.
-
-> [!NOTE]
-> Mbed TLS 2.x and 3.x are supported. The library automatically detects the version and uses the appropriate API.
-
-> [!NOTE]
-> wolfSSL must be built with OpenSSL compatibility layer enabled (`--enable-opensslall`). wolfSSL 5.x is supported.
-
-> [!NOTE]
-> **Mbed TLS / wolfSSL limitation:** `get_ca_certs()` and `get_ca_names()` only reflect CA certificates loaded via `load_ca_cert_store()` or `load_ca_cert_store(pem, size)`. Certificates loaded through `set_ca_cert_path()` or system certificates (`load_system_certs`) are not enumerable with these backends.
-
-> [!TIP]
-> For macOS: cpp-httplib automatically loads system certs from the Keychain when a TLS backend is enabled. `CoreFoundation` and `Security` must be linked with `-framework`. To disable this, define `CPPHTTPLIB_DISABLE_MACOSX_AUTOMATIC_ROOT_CERTIFICATES`.
+> **Mbed TLS / wolfSSL limitation:** `get_ca_certs()` and `get_ca_names()` only reflect CA certificates loaded via `load_ca_cert_store()`. Certificates loaded through `set_ca_cert_path()` or system certificates (`load_system_certs`) are not enumerable.
 
 ```c++
 // Use either OpenSSL, Mbed TLS, or wolfSSL
@@ -197,27 +185,21 @@ svr.Get("/", [](const httplib::Request &req, httplib::Response &res) {
 });
 ```
 
-### Windows Certificate Verification
+### Platform-specific Certificate Handling
 
-On Windows, cpp-httplib automatically performs additional certificate verification using the Windows certificate store via CryptoAPI (`CertGetCertificateChain` / `CertVerifyCertificateChainPolicy`). This works with all TLS backends (OpenSSL, Mbed TLS, and wolfSSL), providing:
+cpp-httplib automatically integrates with the OS certificate store on macOS and Windows. This works with all TLS backends.
 
-- Real-time certificate validation integrated with Windows Update
-- Certificate revocation checking
-- SSL/TLS policy verification using the system certificate store (ROOT and CA)
+| Platform | Behavior | Disable (compile time) |
+| :------- | :------- | :--------------------- |
+| macOS | Loads system certs from Keychain (link `CoreFoundation` and `Security` with `-framework`) | `CPPHTTPLIB_DISABLE_MACOSX_AUTOMATIC_ROOT_CERTIFICATES` |
+| Windows | Verifies certs via CryptoAPI (`CertGetCertificateChain` / `CertVerifyCertificateChainPolicy`) with revocation checking | `CPPHTTPLIB_DISABLE_WINDOWS_AUTOMATIC_ROOT_CERTIFICATES_UPDATE` |
 
-This feature is enabled by default and can be controlled at runtime:
+On Windows, verification can also be disabled at runtime:
 
 ```c++
-// Disable Windows certificate verification (use only OpenSSL/Mbed TLS/wolfSSL verification)
 cli.enable_windows_certificate_verification(false);
 ```
 
-To disable this feature at compile time, define:
-
-```c++
-#define CPPHTTPLIB_DISABLE_WINDOWS_AUTOMATIC_ROOT_CERTIFICATES_UPDATE
-```
-
 > [!NOTE]
 > When using SSL, it seems impossible to avoid SIGPIPE in all cases, since on some operating systems, SIGPIPE can only be suppressed on a per-message basis, but there is no way to make the OpenSSL library do so for its internal communications. If your program needs to avoid being terminated on SIGPIPE, the only fully general way might be to set up a signal handler for SIGPIPE to handle or ignore it yourself.