diff --git a/include/onnxruntime/core/session/onnxruntime_c_api.h b/include/onnxruntime/core/session/onnxruntime_c_api.h
index 176b988ad0..76b325a471 100644
--- a/include/onnxruntime/core/session/onnxruntime_c_api.h
+++ b/include/onnxruntime/core/session/onnxruntime_c_api.h
@@ -6,8 +6,8 @@
 #include <stdint.h>
 #include <string.h>
 
-// This value is used in structures passed to ORT so that a newer version of ORT will still work with
-#define ORT_API_VERSION 1
+// This value is used in structures passed to ORT so that a newer version of ORT will still work with them
+#define ORT_API_VERSION 2
 
 #ifdef __cplusplus
 extern "C" {
@@ -214,6 +214,8 @@ typedef struct OrtApi OrtApi;
 
 struct OrtApiBase {
   const OrtApi*(ORT_API_CALL* GetApi)(uint32_t version)NO_EXCEPTION;  // Pass in ORT_API_VERSION
+  // nullptr will be returned if the version is unsupported, for example when using a runtime older than this header file
+
   const char*(ORT_API_CALL* GetVersionString)() NO_EXCEPTION;
 };
 typedef struct OrtApiBase OrtApiBase;
diff --git a/onnxruntime/core/session/custom_ops.cc b/onnxruntime/core/session/custom_ops.cc
index 0276b167bc..919a398bbc 100644
--- a/onnxruntime/core/session/custom_ops.cc
+++ b/onnxruntime/core/session/custom_ops.cc
@@ -72,7 +72,7 @@ namespace onnxruntime {
 
 struct CustomOpKernel : OpKernel {
   CustomOpKernel(const OpKernelInfo& info, OrtCustomOp& op) : OpKernel(info), op_(op) {
-    if (op_.version != 1)
+    if (op_.version > ORT_API_VERSION)
       throw std::invalid_argument("Unsupported version '" + std::to_string(op_.version) + "' in custom op '" + op.GetName(&op));
     op_kernel_ = op_.CreateKernel(&op_, OrtGetApiBase()->GetApi(op_.version), reinterpret_cast<OrtKernelInfo*>(const_cast<OpKernelInfo*>(&info)));
   }
diff --git a/onnxruntime/core/session/onnxruntime_c_api.cc b/onnxruntime/core/session/onnxruntime_c_api.cc
index b9d4714e00..cf44028e71 100644
--- a/onnxruntime/core/session/onnxruntime_c_api.cc
+++ b/onnxruntime/core/session/onnxruntime_c_api.cc
@@ -1334,7 +1334,49 @@ static constexpr OrtApiBase ort_api_base = {
     &OrtApis::GetVersionString,
 };
 
-static constexpr OrtApi ort_api_1 = {
+/* Rules on how to add a new Ort API version
+
+In general, NEVER remove or rearrange the members in this structure unless a new version is being created. The
+goal is for newer shared libraries of the Onnx Runtime to work with binaries targeting the previous versions.
+In order to do that we need to ensure older binaries get the older interfaces they are expecting.
+
+If the next version of the OrtApi only adds members, new members can be added at the end of the OrtApi structure
+without breaking anything. In this case, rename the ort_api_# structure in a way that shows the range of versions
+it supports, for example 'ort_api_1_to_2', and then GetApi can return the same structure for a range of versions.
+
+If methods need to be removed or rearranged, then make a copy of the OrtApi structure and name it 'OrtApi#to#'.
+The latest Api should always be named just OrtApi. Then make a copy of the latest ort_api_* structure below and
+name it ort_api_# to match the latest version number supported, you'll need to be sure the structure types match
+the API they're for (the compiler should complain if this isn't correct).
+
+If there is no desire to have the headers still expose the older APIs (clutter, documentation, etc) then the
+definition should be moved to a file included by this file so that it's still defined here for binary compatibility
+but isn't visible in public headers.
+
+So for example, if we wanted to just add some new members to the ort_api_1_to_2, we'd take the following steps:
+
+	In include\onnxruntime\core\session\onnxruntime_c_api.h we'd just add the members to the end of the structure
+
+	In this file, we'd correspondingly add the member values to the end of the ort_api_1_to_2 structure, and also rename
+	it to ort_api_1_to_3.
+
+	Then in GetApi we'd make it return ort_api_1_to_3 for versions 1 through 3.
+
+Second example, if we wanted to add and remove some members, we'd do this:
+
+	In include\onnxruntime\core\session\onnxruntime_c_api.h we'd make a copy of the OrtApi structure and name the
+	old one OrtApi1to2. In the new OrtApi we'd add or remove any members that we desire.
+
+	In this file, we'd create a new copy of ort_api_1_to_2 called ort_api_3 and make the corresponding changes that were
+	made to the new OrtApi.
+
+	In GetApi we now make it return ort_api_3 for version 3.
+*/
+
+static constexpr OrtApi ort_api_1_to_2 = {
+    // NOTE: The ordering of these fields MUST not change after that version has shipped since existing binaries depend on this ordering.
+
+    // Shipped as version 1 - DO NOT MODIFY (see above text for more information)
     &OrtApis::CreateStatus,
     &OrtApis::GetErrorCode,
     &OrtApis::GetErrorMessage,
@@ -1449,13 +1491,20 @@ static constexpr OrtApi ort_api_1 = {
     &OrtApis::ReleaseTensorTypeAndShapeInfo,
     &OrtApis::ReleaseSessionOptions,
     &OrtApis::ReleaseCustomOpDomain,
+    // End of Version 1 - DO NOT MODIFY ABOVE (see above text for more information)
+
+    // Version 2 - In development, feel free to add/remove/rearrange here
 };
 
-ORT_API(const OrtApi*, OrtApis::GetApi, uint32_t version) {
-  if (version > 1)
-    return nullptr;
+// Assert to do a limited check to ensure Version 1 of OrtApi never changes (will detect an addition or deletion but not if they cancel out each other)
+// If this assert hits, read the above 'Rules on how to add a new Ort API version'
+static_assert(offsetof(OrtApi, ReleaseCustomOpDomain) / sizeof(void*) == 101, "Size of version 1 API cannot change");
 
-  return &ort_api_1;
+ORT_API(const OrtApi*, OrtApis::GetApi, uint32_t version) {
+  if (version >= 1 && version <= 2)
+    return &ort_api_1_to_2;
+
+  return nullptr;  // Unsupported version
 }
 
 ORT_API(const char*, OrtApis::GetVersionString) {