diff --git a/renderdoc/os/os_specific.h b/renderdoc/os/os_specific.h
index 7e51fd462..88d991b33 100644
--- a/renderdoc/os/os_specific.h
+++ b/renderdoc/os/os_specific.h
@@ -317,7 +317,7 @@ namespace OSUtility
 {
 inline void ForceCrash();
 inline void DebugBreak();
-inline bool DebuggerPresent();
+bool DebuggerPresent();
 enum
 {
   Output_DebugMon,
diff --git a/renderdoc/os/posix/android/android_process.cpp b/renderdoc/os/posix/android/android_process.cpp
index 97356b727..7ae4d63a7 100644
--- a/renderdoc/os/posix/android/android_process.cpp
+++ b/renderdoc/os/posix/android/android_process.cpp
@@ -77,3 +77,46 @@ int GetIdentPort(pid_t childPid)
 
   return ret;
 }
+
+// because OSUtility::DebuggerPresent is called often we want it to be
+// cheap. Opening and parsing a file would cause high overhead on each
+// call, so instead we just cache it at startup. This fails in the case
+// of attaching to processes
+bool debuggerPresent = false;
+
+void CacheDebuggerPresent()
+{
+  FILE *f = FileIO::fopen("/proc/self/status", "r");
+
+  if(f == NULL)
+  {
+    RDCWARN("Couldn't open /proc/self/status");
+    return;
+  }
+
+  // read through the proc file to check for TracerPid
+  while(ret == 0 && !feof(f))
+  {
+    const size_t sz = 512;
+    char line[sz];
+    line[sz - 1] = 0;
+    fgets(line, sz - 1, f);
+
+    int tracerpid = 0;
+    int num = sscanf(line, "TracerPid: %d", &tracerpid);
+
+    // found TracerPid line
+    if(num == 1)
+    {
+      debuggerPresent = (tracerpid != 0);
+      break;
+    }
+  }
+
+  FileIO::fclose(f);
+}
+
+bool OSUtility::DebuggerPresent()
+{
+  return debuggerPresent;
+}
diff --git a/renderdoc/os/posix/apple/apple_process.cpp b/renderdoc/os/posix/apple/apple_process.cpp
index 6d573117d..a8318156f 100644
--- a/renderdoc/os/posix/apple/apple_process.cpp
+++ b/renderdoc/os/posix/apple/apple_process.cpp
@@ -25,6 +25,7 @@
 #include <crt_externs.h>
 #include <sys/sysctl.h>
 #include <sys/types.h>
+#include <unistd.h>
 #include "os/os_specific.h"
 
 char **GetCurrentEnvironment()
@@ -133,3 +134,23 @@ int GetIdentPort(pid_t childPid)
 
   return 0;
 }
+
+void CacheDebuggerPresent()
+{
+}
+
+// from https://developer.apple.com/library/mac/qa/qa1361/_index.html on how to detect the debugger
+bool OSUtility::DebuggerPresent()
+{
+// apple requires that this only be called in debug builds
+#if defined(RELEASE)
+  return false;
+#else
+  int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_PID, getpid()};
+  kinfo_proc info = {};
+  size_t size = sizeof(info);
+  sysctl(mib, ARRAY_COUNT(mib), &info, &size, NULL, 0);
+
+  return info.kp_proc.p_flag & P_TRACED;
+#endif
+}
diff --git a/renderdoc/os/posix/linux/linux_process.cpp b/renderdoc/os/posix/linux/linux_process.cpp
index 97356b727..27f4352dc 100644
--- a/renderdoc/os/posix/linux/linux_process.cpp
+++ b/renderdoc/os/posix/linux/linux_process.cpp
@@ -77,3 +77,46 @@ int GetIdentPort(pid_t childPid)
 
   return ret;
 }
+
+// because OSUtility::DebuggerPresent is called often we want it to be
+// cheap. Opening and parsing a file would cause high overhead on each
+// call, so instead we just cache it at startup. This fails in the case
+// of attaching to processes
+bool debuggerPresent = false;
+
+void CacheDebuggerPresent()
+{
+  FILE *f = FileIO::fopen("/proc/self/status", "r");
+
+  if(f == NULL)
+  {
+    RDCWARN("Couldn't open /proc/self/status");
+    return;
+  }
+
+  // read through the proc file to check for TracerPid
+  while(!feof(f))
+  {
+    const size_t sz = 512;
+    char line[sz];
+    line[sz - 1] = 0;
+    fgets(line, sz - 1, f);
+
+    int tracerpid = 0;
+    int num = sscanf(line, "TracerPid: %d", &tracerpid);
+
+    // found TracerPid line
+    if(num == 1)
+    {
+      debuggerPresent = (tracerpid != 0);
+      break;
+    }
+  }
+
+  FileIO::fclose(f);
+}
+
+bool OSUtility::DebuggerPresent()
+{
+  return debuggerPresent;
+}
diff --git a/renderdoc/os/posix/posix_specific.h b/renderdoc/os/posix/posix_specific.h
index bf8d3a637..cc618d521 100644
--- a/renderdoc/os/posix/posix_specific.h
+++ b/renderdoc/os/posix/posix_specific.h
@@ -46,10 +46,7 @@ inline void DebugBreak()
 {
   raise(SIGTRAP);
 }
-inline bool DebuggerPresent()
-{
-  return true;
-}
+bool DebuggerPresent();
 void WriteOutput(int channel, const char *str);
 };
 
diff --git a/renderdoc/os/posix/posix_threading.cpp b/renderdoc/os/posix/posix_threading.cpp
index de37dbc10..cfa1dd696 100644
--- a/renderdoc/os/posix/posix_threading.cpp
+++ b/renderdoc/os/posix/posix_threading.cpp
@@ -26,6 +26,8 @@
 #include <unistd.h>
 #include "os/os_specific.h"
 
+void CacheDebuggerPresent();
+
 uint64_t Timing::GetUnixTimestamp()
 {
   return (uint64_t)time(NULL);
@@ -128,6 +130,8 @@ void Init()
   int err = pthread_key_create(&OSTLSHandle, NULL);
   if(err != 0)
     RDCFATAL("Can't allocate OS TLS slot");
+
+  CacheDebuggerPresent();
 }
 
 void Shutdown()