diff --git a/sipi/scripts/log_util.lua b/sipi/scripts/log_util.lua
new file mode 100644
index 0000000000..16b1865468
--- /dev/null
+++ b/sipi/scripts/log_util.lua
@@ -0,0 +1,8 @@
+-- * Copyright © 2021 - 2022 Swiss National Data and Service Center for the Humanities and/or DaSCH Service Platform contributors.
+-- * SPDX-License-Identifier: Apache-2.0
+
+function log(msg, level)
+    local timestamp = os.date("!%Y-%m-%dT%H:%M:%S")
+    local log_message = timestamp .. " - " .. msg
+    server.log(log_message, level)
+end
diff --git a/sipi/scripts/sipi.init.lua b/sipi/scripts/sipi.init.lua
index 4ea52dba90..b316c08105 100644
--- a/sipi/scripts/sipi.init.lua
+++ b/sipi/scripts/sipi.init.lua
@@ -2,10 +2,11 @@
 -- * SPDX-License-Identifier: Apache-2.0
 
 require "get_knora_session"
+require "log_util"
 
 -------------------------------------------------------------------------------
--- This function is being called from sipi before the file is served
--- Knora is called to ask for the user's permissions on the file
+-- This function is being called from sipi before the file is served.
+-- DSP-API is called to ask for the user's permissions on the file
 -- Parameters:
 --    prefix: This is the prefix that is given on the IIIF url
 --    identifier: the identifier for the image
@@ -20,7 +21,7 @@ require "get_knora_session"
 --    filepath: server-path where the master file is located
 -------------------------------------------------------------------------------
 function pre_flight(prefix, identifier, cookie)
-    server.log("pre_flight called in sipi.init.lua", server.loglevel.LOG_DEBUG)
+    log("pre_flight called in sipi.init.lua", server.loglevel.LOG_DEBUG)
 
     if config.prefix_as_path then
         filepath = config.imgroot .. '/' .. prefix .. '/' .. identifier
@@ -28,6 +29,8 @@ function pre_flight(prefix, identifier, cookie)
         filepath = config.imgroot .. '/' .. identifier
     end
 
+    log("pre_flight - filepath: " .. filepath, server.loglevel.LOG_DEBUG)
+
     if prefix == "thumbs" then
         -- always allow thumbnails
         return 'allow', filepath
@@ -38,21 +41,22 @@ function pre_flight(prefix, identifier, cookie)
         return 'allow', filepath
     end
 
-    knora_cookie_header = nil
+    dsp_cookie_header = nil
 
     if cookie ~= '' then
 
-        -- tries to extract the Knora session name and id from the cookie:
+        -- tries to extract the DSP session name and id from the cookie:
         -- gets the digits between "sid=" and the closing ";" (only given in case of several key value pairs)
         -- returns nil if it cannot find it
         session = get_session_id(cookie)
 
         if session == nil or session["name"] == nil or session["id"] == nil then
             -- no session could be extracted
-            server.log("cookie key is invalid: " .. cookie, server.loglevel.LOG_ERR)
+            log("cookie key is invalid: " .. cookie, server.loglevel.LOG_ERR)
         else
-            knora_cookie_header = { Cookie = session["name"] .. "=" .. session["id"] }
-            server.log("pre_flight - knora_cookie_header: " .. knora_cookie_header["Cookie"], server.loglevel.LOG_DEBUG)
+            dsp_cookie_header = { Cookie = session["name"] .. "=" .. session["id"] }
+            log("pre_flight - dsp_cookie_header: " ..
+                dsp_cookie_header["Cookie"], server.loglevel.LOG_DEBUG)
         end
     end
 
@@ -63,7 +67,8 @@ function pre_flight(prefix, identifier, cookie)
     if webapi_hostname == nil then
         webapi_hostname = config.knora_path
     end
-    server.log("webapi_hostname: " .. webapi_hostname, server.loglevel.LOG_DEBUG)
+    log("pre_flight - webapi_hostname: " .. webapi_hostname,
+        server.loglevel.LOG_DEBUG)
 
     --
     -- Allows to set SIPI_WEBAPI_PORT environment variable and use its value.
@@ -72,36 +77,39 @@ function pre_flight(prefix, identifier, cookie)
     if webapi_port == nil then
         webapi_port = config.knora_port
     end
-    server.log("webapi_port: " .. webapi_port, server.loglevel.LOG_DEBUG)
+    log("pre_flight - webapi_port: " .. webapi_port, server.loglevel.LOG_DEBUG)
 
-    knora_url = 'http://' .. webapi_hostname .. ':' .. webapi_port .. '/admin/files/' .. prefix .. '/' .. identifier
+    api_url = 'http://' .. webapi_hostname .. ':' .. webapi_port .. '/admin/files/' .. prefix .. '/' .. identifier
 
-    -- print("knora_url: " .. knora_url)
-    server.log("pre_flight - knora_url: " .. knora_url, server.loglevel.LOG_DEBUG)
+    log("pre_flight - api_url: " .. api_url, server.loglevel.LOG_DEBUG)
 
-    success, result = server.http("GET", knora_url, knora_cookie_header, 5000)
+    success, result = server.http("GET", api_url, dsp_cookie_header, 5000)
 
     -- check HTTP request was successful
     if not success then
-        server.log("Server.http() failed: " .. result, server.loglevel.LOG_ERR)
+        log("pre_flight - Server.http() failed: " .. result,
+            server.loglevel.LOG_ERR)
         return 'deny'
     end
 
     if result.status_code ~= 200 then
-        server.log("Knora returned HTTP status code " .. result.status_code, server.loglevel.LOG_ERR)
-        server.log(result.body, server.loglevel.LOG_ERR)
+        log("pre_flight - DSP-API returned HTTP status code " ..
+            result.status_code, server.loglevel.LOG_ERR)
+        log("result body: " .. result.body, server.loglevel.LOG_ERR)
         return 'deny'
     end
 
-    server.log("pre_flight - response body: " .. tostring(result.body), server.loglevel.LOG_DEBUG)
+    log("pre_flight - response body: " .. tostring(result.body),
+        server.loglevel.LOG_DEBUG)
 
     success, response_json = server.json_to_table(result.body)
     if not success then
-        server.log("Server.http() failed: " .. response_json, server.loglevel.LOG_ERR)
+        log("Server.http() failed: " .. response_json, server.loglevel.LOG_ERR)
         return 'deny'
     end
 
-    server.log("pre_flight - permission code: " .. response_json.permissionCode, server.loglevel.LOG_DEBUG)
+    log("pre_flight - permission code: " .. response_json.permissionCode,
+        server.loglevel.LOG_DEBUG)
 
     if response_json.permissionCode == 0 then
         -- no view permission on file
@@ -114,18 +122,21 @@ function pre_flight(prefix, identifier, cookie)
         local restrictedViewSize
 
         if response_json.restrictedViewSettings ~= nil then
-            -- server.log("pre_flight - restricted view settings - watermark: " .. tostring(response_json.restrictedViewSettings.watermark), server.loglevel.LOG_DEBUG)
+            log("pre_flight - restricted view settings - watermark: " ..
+                tostring(response_json.restrictedViewSettings.watermark), server.loglevel.LOG_DEBUG)
 
             if response_json.restrictedViewSettings.size ~= nil then
-                server.log("pre_flight - restricted view settings - size: " ..
+                log("pre_flight - restricted view settings - size: " ..
                     tostring(response_json.restrictedViewSettings.size), server.loglevel.LOG_DEBUG)
                 restrictedViewSize = response_json.restrictedViewSettings.size
             else
-                server.log("pre_flight - using default restricted view size", server.loglevel.LOG_DEBUG)
+                log("pre_flight - using default restricted view size",
+                    server.loglevel.LOG_DEBUG)
                 restrictedViewSize = config.thumb_size
             end
         else
-            server.log("pre_flight - using default restricted view size", server.loglevel.LOG_DEBUG)
+            log("pre_flight - using default restricted view size",
+                server.loglevel.LOG_DEBUG)
             restrictedViewSize = config.thumb_size
         end