diff --git a/src/substrait/common/Io.cpp b/src/substrait/common/Io.cpp
index 475c49f1..7055160c 100644
--- a/src/substrait/common/Io.cpp
+++ b/src/substrait/common/Io.cpp
@@ -2,6 +2,7 @@
 
 #include "substrait/common/Io.h"
 
+#include <regex>
 #include <string_view>
 
 #include "substrait/textplan/converter/LoadBinary.h"
@@ -10,35 +11,47 @@
 
 namespace io::substrait {
 
+namespace {
+
+const std::regex kIsJson(R"(("extensionUris"|"extensions"|"relations"))");
+const std::regex kIsProtoText(R"(potatoes)");
+const std::regex kIsText(
+    R"((^|\n) *(pipelines|[a-z]+ *relation|schema|source|extension_space) *)");
+
+PlanFileEncoding detectEncoding(std::string_view content) {
+  if (std::regex_search(content.begin(), content.end(), kIsJson)) {
+    return kJson;
+  }
+  if (std::regex_search(content.begin(), content.end(), kIsProtoText)) {
+    return kProtoText;
+  }
+  if (std::regex_search(content.begin(), content.end(), kIsText)) {
+    return kText;
+  }
+  return kBinary;
+}
+
+} // namespace
+
 absl::StatusOr<::substrait::proto::Plan> loadPlanWithUnknownEncoding(
     std::string_view input_filename) {
-  // TODO -- Add logic to detect the file type before trying to load it.
   auto contentOrError = textplan::readFromFile(input_filename);
   if (!contentOrError.ok()) {
     return contentOrError.status();
   }
 
-  auto planOrError = textplan::loadFromJson(*contentOrError);
-  if (planOrError.ok()) {
-    return *planOrError;
-  }
-
-  planOrError = textplan::loadFromProtoText(*contentOrError);
-  if (planOrError.ok()) {
-    return *planOrError;
-  }
-
-  planOrError = textplan::loadFromText(*contentOrError);
-  if (planOrError.ok()) {
-    return *planOrError;
-  }
-
-  planOrError = textplan::loadFromBinary(*contentOrError);
-  if (planOrError.ok()) {
-    return *planOrError;
+  auto encoding = detectEncoding(*contentOrError);
+  absl::StatusOr<::substrait::proto::Plan> planOrError;
+  switch (encoding) {
+    case kBinary:
+      return textplan::loadFromBinary(*contentOrError);
+    case kJson:
+      return textplan::loadFromJson(*contentOrError);
+    case kProtoText:
+      return textplan::loadFromProtoText(*contentOrError);
+    case kText:
+      return textplan::loadFromText(*contentOrError);
   }
-
-  return planOrError.status();
 }
 
 absl::Status savePlan(
diff --git a/src/substrait/common/tests/IoTest.cpp b/src/substrait/common/tests/IoTest.cpp
index 61c7631f..eec65562 100644
--- a/src/substrait/common/tests/IoTest.cpp
+++ b/src/substrait/common/tests/IoTest.cpp
@@ -5,6 +5,7 @@
 #include <gmock/gmock-matchers.h>
 #include <gtest/gtest.h>
 #include <protobuf-matchers/protocol-buffer-matchers.h>
+#include <unistd.h>
 
 using ::protobuf_matchers::EqualsProto;
 using ::protobuf_matchers::Partially;
@@ -40,10 +41,25 @@ TEST_F(IoTest, LoadMissingFile) {
 }
 
 class SaveAndLoadTestFixture
-    : public ::testing::TestWithParam<PlanFileEncoding> {};
+    : public ::testing::TestWithParam<PlanFileEncoding> {
+ public:
+  ~SaveAndLoadTestFixture() override {
+    for (const auto& filename : testFiles_) {
+      unlink(filename.c_str());
+    }
+  }
+
+  void registerCleanup(const char* filename) {
+    testFiles_.emplace_back(filename);
+  }
+
+ private:
+  std::vector<std::string> testFiles_;
+};
 
 TEST_P(SaveAndLoadTestFixture, SaveAndLoad) {
   auto tempFilename = std::tmpnam(nullptr);
+  registerCleanup(tempFilename);
   PlanFileEncoding encoding = GetParam();
 
   ::substrait::proto::Plan plan;
@@ -51,10 +67,10 @@ TEST_P(SaveAndLoadTestFixture, SaveAndLoad) {
   auto read = root->mutable_input()->mutable_read();
   read->mutable_named_table()->add_names("table_name");
   auto status = ::io::substrait::savePlan(plan, tempFilename, encoding);
-  ASSERT_TRUE(status.ok()) << status;
+  ASSERT_TRUE(status.ok()) << "Save failed.\n" << status;
 
   auto result = ::io::substrait::loadPlanWithUnknownEncoding(tempFilename);
-  ASSERT_TRUE(result.ok()) << result.status();
+  ASSERT_TRUE(result.ok()) << "Load failed.\n" << result.status();
   ASSERT_THAT(
       *result,
       Partially(EqualsProto<::substrait::proto::Plan>(