diff --git a/dom/canvas/WebGL2Context.cpp b/dom/canvas/WebGL2Context.cpp
index f9a1eba4bff9..73083c964c81 100644
--- a/dom/canvas/WebGL2Context.cpp
+++ b/dom/canvas/WebGL2Context.cpp
@@ -138,7 +138,7 @@ WebGLContext::InitWebGL2(FailureReason* const out_failReason)
 
     ////
 
-    if (missingList.size()) {
+    if (!missingList.empty()) {
         nsAutoCString exts;
         for (auto itr = missingList.begin(); itr != missingList.end(); ++itr) {
             exts.AppendLiteral("\n  ");
diff --git a/dom/canvas/WebGLBuffer.cpp b/dom/canvas/WebGLBuffer.cpp
index e8d883ff1958..c278c2721513 100644
--- a/dom/canvas/WebGLBuffer.cpp
+++ b/dom/canvas/WebGLBuffer.cpp
@@ -160,7 +160,7 @@ WebGLBuffer::BufferData(GLenum target, size_t size, const void* data, GLenum usa
     mIndexCache = Move(newIndexCache);
 
     if (mIndexCache) {
-        if (mIndexRanges.size()) {
+        if (!mIndexRanges.empty()) {
             mContext->GeneratePerfWarning("[%p] Invalidating %u ranges.", this,
                                           uint32_t(mIndexRanges.size()));
             mIndexRanges.clear();
@@ -251,7 +251,7 @@ WebGLBuffer::InvalidateCacheRange(size_t byteOffset, size_t byteLength) const
         invalids.push_back(range);
     }
 
-    if (invalids.size()) {
+    if (!invalids.empty()) {
         mContext->GeneratePerfWarning("[%p] Invalidating %u/%u ranges.", this,
                                       uint32_t(invalids.size()),
                                       uint32_t(mIndexRanges.size()));
diff --git a/dom/canvas/WebGLContextDraw.cpp b/dom/canvas/WebGLContextDraw.cpp
index 92ca2ea89aa6..512a25ad5c14 100644
--- a/dom/canvas/WebGLContextDraw.cpp
+++ b/dom/canvas/WebGLContextDraw.cpp
@@ -164,7 +164,7 @@ ScopedResolveTexturesForDraw::ScopedResolveTexturesForDraw(WebGLContext* webgl,
 
 ScopedResolveTexturesForDraw::~ScopedResolveTexturesForDraw()
 {
-    if (!mRebindRequests.size())
+    if (mRebindRequests.empty())
         return;
 
     gl::GLContext* gl = mWebGL->gl;
diff --git a/dom/canvas/WebGLProgram.cpp b/dom/canvas/WebGLProgram.cpp
index 365b8e178af8..6f7198bc7d89 100644
--- a/dom/canvas/WebGLProgram.cpp
+++ b/dom/canvas/WebGLProgram.cpp
@@ -1263,7 +1263,7 @@ WebGLProgram::ValidateAfterTentativeLink(nsCString* const out_linkLog) const
     // * Unrecognized varying name
     // * Duplicate varying name
     // * Too many components for specified buffer mode
-    if (mNextLink_TransformFeedbackVaryings.size()) {
+    if (!mNextLink_TransformFeedbackVaryings.empty()) {
         GLuint maxComponentsPerIndex = 0;
         switch (mNextLink_TransformFeedbackBufferMode) {
         case LOCAL_GL_INTERLEAVED_ATTRIBS:
@@ -1283,7 +1283,7 @@ WebGLProgram::ValidateAfterTentativeLink(nsCString* const out_linkLog) const
         std::vector<size_t> componentsPerVert;
         std::set<const WebGLActiveInfo*> alreadyUsed;
         for (const auto& wideUserName : mNextLink_TransformFeedbackVaryings) {
-            if (!componentsPerVert.size() ||
+            if (componentsPerVert.empty() ||
                 mNextLink_TransformFeedbackBufferMode == LOCAL_GL_SEPARATE_ATTRIBS)
             {
                 componentsPerVert.push_back(0);
@@ -1608,7 +1608,7 @@ webgl::LinkedProgramInfo::MapFragDataName(const nsCString& userName,
 {
     // FS outputs can be arrays, but not structures.
 
-    if (!fragDataMap.size()) {
+    if (fragDataMap.empty()) {
         // No mappings map from validation, so just forward it.
         *out_mappedName = userName;
         return true;
diff --git a/dom/canvas/WebGLTransformFeedback.cpp b/dom/canvas/WebGLTransformFeedback.cpp
index 78e36653155a..da1b9986964f 100644
--- a/dom/canvas/WebGLTransformFeedback.cpp
+++ b/dom/canvas/WebGLTransformFeedback.cpp
@@ -62,7 +62,7 @@ WebGLTransformFeedback::BeginTransformFeedback(GLenum primMode)
     const auto& prog = mContext->mCurrentProgram;
     if (!prog ||
         !prog->IsLinked() ||
-        !prog->LinkInfo()->componentsPerTFVert.size())
+        prog->LinkInfo()->componentsPerTFVert.empty())
     {
         mContext->ErrorInvalidOperation("%s: Current program not valid for transform"
                                         " feedback.",