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diff --git a/src/Text/Pandoc/Class/IO/HTTP.hs b/src/Text/Pandoc/Class/IO/HTTP.hs
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+++ b/src/Text/Pandoc/Class/IO/HTTP.hs
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+{-# LANGUAGE CPP #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE OverloadedStrings #-}
+{- |
+Module      : Text.Pandoc.Class.IO.HTTP
+Copyright   : Copyright (C) 2025 John MacFarlane
+License     : GNU GPL, version 2 or above
+
+Maintainer  : John MacFarlane <[email protected]>
+Stability   : alpha
+Portability : portable
+
+HTTP fetching functionality for pandoc.
+-}
+module Text.Pandoc.Class.IO.HTTP
+  ( openURL
+  ) where
+
+import Network.URI (URI(..), parseURI)
+import Data.Text (Text)
+import Control.Monad.IO.Class (MonadIO)
+import Text.Pandoc.Class.PandocMonad (PandocMonad, extractURIData)
+import Text.Pandoc.Error (PandocError (..))
+import Text.Pandoc.MIME (MimeType)
+import qualified Data.ByteString as B
+import qualified Data.Text as T
+import Control.Monad.Except (throwError)
+#ifdef PANDOC_HTTP_SUPPORT
+import Data.ByteString.Lazy (toChunks)
+import Control.Monad.IO.Class (liftIO)
+import System.Environment (getEnv)
+import Data.Default (def)
+import Network.Connection (TLSSettings(..))
+import qualified Network.TLS as TLS
+import qualified Network.TLS.Extra as TLS
+import System.X509 (getSystemCertificateStore)
+import Network.HTTP.Client
+       (httpLbs, Manager, responseBody, responseHeaders,
+        Request(port, host, requestHeaders), parseUrlThrow, newManager, HttpException)
+import Network.HTTP.Client.Internal (addProxy)
+import Network.HTTP.Client.TLS (mkManagerSettings)
+import Network.HTTP.Types.Header ( hContentType )
+import Network.Socket (withSocketsDo)
+import Text.Pandoc.Class.CommonState (CommonState (..))
+import Text.Pandoc.Class.PandocMonad ( getsCommonState, modifyCommonState, report )
+import qualified Data.CaseInsensitive as CI
+import System.IO.Error
+import Text.Pandoc.Logging (LogMessage (..))
+import qualified Control.Exception as E
+import qualified Text.Pandoc.UTF8 as UTF8
+#endif
+
+#ifdef PANDOC_HTTP_SUPPORT
+getManager :: (PandocMonad m, MonadIO m) => m Manager
+getManager = do
+  mbManager <- getsCommonState stManager
+  disableCertificateValidation <- getsCommonState stNoCheckCertificate
+  case mbManager of
+    Just manager -> pure manager
+    Nothing -> do
+      manager <- liftIO $ do
+        certificateStore <- getSystemCertificateStore
+        let tlsSettings = TLSSettings $
+               (TLS.defaultParamsClient "localhost.localdomain" "80")
+                  { TLS.clientSupported = def{ TLS.supportedCiphers =
+                                               TLS.ciphersuite_default
+                                             , TLS.supportedExtendedMainSecret =
+                                                TLS.AllowEMS }
+                  , TLS.clientShared = def
+                      { TLS.sharedCAStore = certificateStore
+                      , TLS.sharedValidationCache =
+                          if disableCertificateValidation
+                             then TLS.ValidationCache
+                                   (\_ _ _ -> return TLS.ValidationCachePass)
+                                   (\_ _ _ -> return ())
+                             else def
+                      }
+                  }
+        let tlsManagerSettings = mkManagerSettings tlsSettings  Nothing
+        newManager tlsManagerSettings
+      modifyCommonState $ \st -> st{ stManager = Just manager }
+      pure manager
+#endif
+
+openURL :: (PandocMonad m, MonadIO m) => Text -> m (B.ByteString, Maybe MimeType)
+openURL u
+ | Just (URI{ uriScheme = "data:",
+              uriPath = upath }) <- parseURI (T.unpack u)
+     = pure $ extractURIData upath
+#ifdef PANDOC_HTTP_SUPPORT
+ | otherwise = do
+     let toReqHeader (n, v) = (CI.mk (UTF8.fromText n), UTF8.fromText v)
+     customHeaders <- map toReqHeader <$> getsCommonState stRequestHeaders
+     report $ Fetching u
+     manager <- getManager
+     res <- liftIO $ E.try $ withSocketsDo $ do
+       proxy <- tryIOError (getEnv "http_proxy")
+       let addProxy' x = case proxy of
+                            Left _ -> return x
+                            Right pr -> parseUrlThrow pr >>= \r ->
+                                return (addProxy (host r) (port r) x)
+       req <- parseUrlThrow (T.unpack u) >>= addProxy'
+       let req' = req{requestHeaders = customHeaders ++ requestHeaders req}
+       resp <- httpLbs req' manager
+       return (B.concat $ toChunks $ responseBody resp,
+               UTF8.toText `fmap` lookup hContentType (responseHeaders resp))
+
+     case res of
+          Right r -> return r
+          Left (e :: HttpException)
+                  -> throwError $ PandocHttpError u (T.pack (show e))
+#else
+ | otherwise =
+     throwError $ PandocHttpError u "pandoc was compiled without HTTP support"
+#endif