As admin, enable "Enable web services for mobile devices": Site administration ► Advanced features Install Spanish additional language packs in your site via Site administration ► Language ► Language packs Search for Spanish (international) and install it Create or use an existing student user in the platform (no admin) Create a Token in the mobile app service for the student user: Click on Site administration ► Server ► Web services ► Manage tokens Create a "User profile field": Site administration ► Users ► Accounts ►  User profile fields ► Create a new profile field Select and create a checkbox Put this HTML in the Name of the profile field to add the multilang filter in it:  <span lang="en" class="multilang">Check in english</span><span lang="es" class="multilang">Check en español</span> Enable Multilang filter: Site administration ► Plugins ► Filters ► Manage filters ► Multi-language content Enable it and set "Apply to" to "Content and headings" Go to the student profile and check if the filter is working The profile field name must see just: Check in english TESTING THE WEB SERVICES Do the CURL REST calling simulating a WS client with the student user. You need to replace the wstoken, studentemail is the email from the student, and the URL of your moodle instance curl 'MOODLE_URL/webservice/rest/server.php?moodlewsrestformat=json' --data 'wsfunction=core_user_get_users_by_field&wstoken=$wstoken&field=email&values[]=$studentemail' --compressed Confirm that: You receive the student object in the response The "customfields" contains the field with type "checkbox" and the "name" is: Check in english Now add the moodlewssettingfilter param as true in the request to enable the filtering in the request, and moodlewssettinglang to specify we want the contents in English. curl 'MOODLE_URL/webservice/rest/server.php?moodlewsrestformat=json' --data 'wsfunction=core_user_get_users_by_field&wstoken=$wstoken&field=email&values[]=$studentemail&moodlewssettingfilter=true&moodlewssettinglang=en' --compressed Confirm that: You receive the student object in the response The "customfields" contains the a field with type "checkbox" and the "name" is: Check in english Now repeat the request but changing the value of moodlewssettinglang to 'es'. curl 'MOODLE_URL/webservice/rest/server.php?moodlewsrestformat=json' --data 'wsfunction=core_user_get_users_by_field&wstoken=$wstoken&field=email&values[]=$studentemail&moodlewssettingfilter=true&moodlewssettinglang=es' --compressed Confirm that: You receive the student object in the response The "customfields" contains the a field with type "checkbox" and the "name" is: Check en español Now we'll do the same for WS core_user_get_course_user_profiles. Create an empty or testing course and enrol the student user in it. Save the course id to use in the request Do the CURL REST calling simulating a WS client with the student user.  You need to replace the $wstoken, $userid and $courseid, and the URL of your moodle instance curl 'MOODLE_URL/webservice/rest/server.php?moodlewsrestformat=json' --data 'wsfunction=core_user_get_course_user_profiles&wstoken=$wstoken&userlist%5B0%5D%5Buserid%5D=$userid&userlist%5B0%5D%5Bcourseid%5D=$courseid&moodlewssettingfilter=false' --compressed Confirm that: You receive the student object in the response The "customfields" contains the a field with type "checkbox" and the "name" is: Check in english Now set the moodlewssettingfilter param as true in the request to enable the filtering in the request, and moodlewssettinglang to specify we want the contents in English. curl 'MOODLE_URL/webservice/rest/server.php?moodlewsrestformat=json' --data 'wsfunction=core_user_get_course_user_profiles&wstoken=$wstoken&userlist%5B0%5D%5Buserid%5D=$userid&userlist%5B0%5D%5Bcourseid%5D=$courseid&moodlewssettingfilter=true&moodlewssettinglang=en' --compressed Confirm that: You receive the student object in the response The "customfields" contains the a field with type "checkbox" and the "name" is: Check in english Now repeat the request but changing the value of moodlewssettinglang to 'es'. curl 'MOODLE_URL/webservice/rest/server.php?moodlewsrestformat=json' --data 'wsfunction=core_user_get_course_user_profiles&wstoken=$wstoken&userlist%5B0%5D%5Buserid%5D=$userid&userlist%5B0%5D%5Bcourseid%5D=$courseid&moodlewssettingfilter=true&moodlewssettinglang=es' --compressed Confirm that: You receive the student object in the response The "customfields" contains the a field with type "checkbox" and the "name" is: Check en español