diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,9 @@
 # ChangeLog for yesod-core
 
+## 1.6.18.6
+
+* Update documentation from `HandlerT` to `HandlerFor` [#1703](https://github.com/yesodweb/yesod/pull/1703)
+
 ## 1.6.18.5
 
 Document `ErrorResponse` [#1698](https://github.com/yesodweb/yesod/pull/1698)
diff --git a/src/Yesod/Core/Handler.hs b/src/Yesod/Core/Handler.hs
--- a/src/Yesod/Core/Handler.hs
+++ b/src/Yesod/Core/Handler.hs
@@ -1464,8 +1464,8 @@
 
 -- | Use a @Source@ for the response body.
 --
--- Note that, for ease of use, the underlying monad is a @HandlerT@. This
--- implies that you can run any @HandlerT@ action. However, since a streaming
+-- Note that, for ease of use, the underlying monad is a @HandlerFor@. This
+-- implies that you can run any @HandlerFor@ action. However, since a streaming
 -- response occurs after the response headers have already been sent, some
 -- actions make no sense here. For example: short-circuit responses, setting
 -- headers, changing status codes, etc.
@@ -1476,8 +1476,8 @@
               -> HandlerFor site TypedContent
 respondSource ctype src = HandlerFor $ \hd ->
     -- Note that this implementation relies on the fact that the ResourceT
-    -- environment provided by the server is the same one used in HandlerT.
-    -- This is a safe assumption assuming the HandlerT is run correctly.
+    -- environment provided by the server is the same one used in HandlerFor.
+    -- This is a safe assumption assuming the HandlerFor is run correctly.
     return $ TypedContent ctype $ ContentSource
            $ transPipe (lift . flip unHandlerFor hd) src
 
diff --git a/src/Yesod/Core/Internal/Run.hs b/src/Yesod/Core/Internal/Run.hs
--- a/src/Yesod/Core/Internal/Run.hs
+++ b/src/Yesod/Core/Internal/Run.hs
@@ -181,7 +181,7 @@
     (fmap ((mempty, ) . HCError) . toErrorHandler)
 
 -- | Function used internally by Yesod in the process of converting a
--- 'HandlerT' into an 'Application'. Should not be needed by users.
+-- 'HandlerFor' into an 'Application'. Should not be needed by users.
 runHandler :: ToTypedContent c
            => RunHandlerEnv site site
            -> HandlerFor site c
@@ -216,26 +216,26 @@
         (toContent ("Internal Server Error" :: S.ByteString))
         (reqSession req)
 
--- | Run a 'HandlerT' completely outside of Yesod.  This
+-- | Run a 'HandlerFor' completely outside of Yesod.  This
 -- function comes with many caveats and you shouldn't use it
 -- unless you fully understand what it's doing and how it works.
 --
 -- As of now, there's only one reason to use this function at
--- all: in order to run unit tests of functions inside 'HandlerT'
+-- all: in order to run unit tests of functions inside 'HandlerFor'
 -- but that aren't easily testable with a full HTTP request.
 -- Even so, it's better to use @wai-test@ or @yesod-test@ instead
 -- of using this function.
 --
 -- This function will create a fake HTTP request (both @wai@'s
 -- 'Request' and @yesod@'s 'Request') and feed it to the
--- @HandlerT@.  The only useful information the @HandlerT@ may
+-- @HandlerFor@.  The only useful information the @HandlerFor@ may
 -- get from the request is the session map, which you must supply
 -- as argument to @runFakeHandler@.  All other fields contain
 -- fake information, which means that they can be accessed but
 -- won't have any useful information.  The response of the
--- @HandlerT@ is completely ignored, including changes to the
+-- @HandlerFor@ is completely ignored, including changes to the
 -- session, cookies or headers.  We only return you the
--- @HandlerT@'s return value.
+-- @HandlerFor@'s return value.
 runFakeHandler :: (Yesod site, MonadIO m) =>
                   SessionMap
                -> (site -> Logger)
diff --git a/src/Yesod/Core/Types.hs b/src/Yesod/Core/Types.hs
--- a/src/Yesod/Core/Types.hs
+++ b/src/Yesod/Core/Types.hs
@@ -231,7 +231,7 @@
 
 -- | An extension of the basic WAI 'W.Application' datatype to provide extra
 -- features needed by Yesod. Users should never need to use this directly, as
--- the 'HandlerT' monad and template haskell code should hide it away.
+-- the 'HandlerFor' monad and template haskell code should hide it away.
 type YesodApp = YesodRequest -> ResourceT IO YesodResponse
 
 -- | A generic widget, allowing specification of both the subsite and master
@@ -473,7 +473,7 @@
 instance MonadLoggerIO (WidgetFor site) where
     askLoggerIO = WidgetFor $ return . rheLog . handlerEnv . wdHandler
 
--- Instances for HandlerT
+-- Instances for HandlerFor
 instance Applicative (HandlerFor site) where
     pure = HandlerFor . const . return
     (<*>) = ap
diff --git a/yesod-core.cabal b/yesod-core.cabal
--- a/yesod-core.cabal
+++ b/yesod-core.cabal
@@ -1,5 +1,5 @@
 name:            yesod-core
-version:         1.6.18.5
+version:         1.6.18.6
 license:         MIT
 license-file:    LICENSE
 author:          Michael Snoyman <michael@snoyman.com>