diff --git a/docs/reference/configuration/mbed_targets.md b/docs/reference/configuration/mbed_targets.md
index 1c2b7183eb..b7b0d146e9 100644
--- a/docs/reference/configuration/mbed_targets.md
+++ b/docs/reference/configuration/mbed_targets.md
@@ -192,7 +192,15 @@ Enabling `is_disk_virtual` adds delay after flashing firmware binary to make sur
 
 #### supported_toolchains
 
-The `supported_toolchains` property is the list of toolchains that support a target. The allowed values for `supported_toolchains` are `ARM`, `uARM`, `ARMC6`, `GCC_ARM` and `IAR`.
+The `supported_toolchains` property is the list of toolchains that support a target. The allowed values for `supported_toolchains` are `ARM`, `uARM`, `ARMC5`, `ARMC6`, `GCC_ARM` and `IAR`.
+
+If you specify `ARMC5` in `supported_toolchains`, it means the corresponding target supports `Arm Compiler 5.06 update 6`.
+
+If a target lists both `ARMC5` and `ARM` (or `ARMC6`) in `supported_toolchains`, the Arm Compiler 6.11 will be used when compiling with `ARM` option for `--toolchain`.
+
+<span class="notes">**Note:** Although you can specify `ARMC5` in `supported_toolchains` in `targets.json`, it's not a valid option for `--toolchain` when compiling using [Mbed CLI](../tools/developing-mbed-cli.html).
+Arm Compiler 6 is the default ARM toolchain for Mbed OS developmet. Most Mbed OS platforms are already compatible with Arm Compiler 6. Some existing targets still supporting Arm Compiler 5 will be migrated to Arm Compiler 6 in the future. Please be aware that you must use Arm Compiler 6 for future development, and we will validate all code contributions to Mbed OS Arm Compiler 6.
+</span>
 
 #### default_toolchain
 
@@ -427,3 +435,7 @@ The `orphans` command shows all targets that you cannot reach from a public targ
 - EFR32MG1P132F256GM48
 - EFR32MG1_BRD4150
 ```
+
+### Related content
+
+- [Developing: Mbed CLI](../tools/developing-mbed-cli.html).
diff --git a/docs/tools/tools_intro.md b/docs/tools/tools_intro.md
index a8491f0078..cd31c66e2b 100644
--- a/docs/tools/tools_intro.md
+++ b/docs/tools/tools_intro.md
@@ -21,23 +21,26 @@ We created the Mbed command-line tool (Mbed CLI), a Python-based tool, specifica
 
 Mbed OS 5 can be built with various toolchains. The currently supported versions are:
 
-- [Arm compiler 5.06 update 6](https://developer.arm.com/products/software-development-tools/compilers/arm-compiler-5/downloads).
+- [Arm compiler 6.11](https://developer.arm.com/products/software-development-tools/compilers/arm-compiler/downloads/version-6).
 - [GNU Arm Embedded version  6 (6-2017-q1-update)](https://developer.arm.com/open-source/gnu-toolchain/gnu-rm/downloads).
-- [IAR Embedded Workbench 8.32](https://www.iar.com/iar-embedded-workbench/tools-for-arm/arm-cortex-m-edition/).
+- [IAR Embedded Workbench 8.32.1](https://www.iar.com/iar-embedded-workbench/tools-for-arm/arm-cortex-m-edition/).
 
 ##### Arm Mbed Online Compiler
 
-The Mbed Online Compiler is our in-house IDE, and should be familiar to anyone who's been working with Mbed for a while. It switches the backing toolchain based on the architecture version:
+The Mbed Online Compiler is our in-house IDE and should be familiar to anyone who's been working with Mbed for a while. It switches the backing toolchain based on the architecture version:
 
 | Architecture version | Compiler |
 |----                  |----           |
-| Arm v6M       | Arm Compiler 5.06 update 6 |
-| Arm v7M       | Arm Compiler 5.06 update 6 |
-| Arm v7A       | Arm Compiler 5.06 update 6 |
-| Arm v8M       | Arm Compiler 6.10.1 |
+| Arm v6M       | `Arm Compiler 6.11` or `Arm Compiler 5.06 update 6` based on the ARM toolchain supported by the target (see `supported_toolchains` in [Adding and configuring targets](../reference/configuration/mbed_targets.html#)) |
+| Arm v7M       | `Arm Compiler 6.11` or `Arm Compiler 5.06 update 6` based on the ARM toolchain supported by the target (see `supported_toolchains` in [Adding and configuring targets](../reference/configuration/mbed_targets.html#)) |
+| Arm v7A       | `Arm Compiler 6.11` |
+| Arm v8M       | `Arm Compiler 6.11` |
 
 For more information, please see the [Online Compiler page](developing-mbed-online-compiler.html).
 
+<span class="note"> **Note:** Arm Compiler 6 is the default ARM toolchain for Mbed OS developmet. Most Mbed OS platforms are already compatible with Arm Compiler 6. Some existing targets still supporting Arm Compiler 5 will also be migrated to ARM Compiler 6 in the future. Please be aware that you must use Arm Compiler 6 for future development, and we will validate all code contributions to Mbed OS with Arm Compiler 6. </span>
+
 ##### Third party development tools
 
 You can export your project from any of our tools to third party tools. For instructions, as well as tool-specific information, see [the Exporting to third party toolchains page](exporting.html).
+