diff --git a/lib/REST/TinyTinyRSS/API.php b/lib/REST/TinyTinyRSS/API.php
index a8e3e8de..0db6601c 100644
--- a/lib/REST/TinyTinyRSS/API.php
+++ b/lib/REST/TinyTinyRSS/API.php
@@ -6,11 +6,24 @@ use JKingWeb\Arsse\Arsse;
 use JKingWeb\Arsse\User;
 use JKingWeb\Arsse\Service;
 use JKingWeb\Arsse\Misc\Context;
+use JKingWeb\Arsse\Misc\ValueInfo;
 use JKingWeb\Arsse\AbstractException;
 use JKingWeb\Arsse\Db\ExceptionInput;
 use JKingWeb\Arsse\Feed\Exception as FeedException;
 use JKingWeb\Arsse\REST\Response;
 
+/*
+
+Protocol difference so far:
+    - handling of incorrect Content-Type and/or HTTP method is different
+    - TT-RSS accepts whitespace-only names; we do not
+    - TT-RSS allows two folders to share the same name under the same parent; we do not
+    - Session lifetime is much shorter by default (does TT-RSS even expire sessions?)
+
+*/
+
+
+
 class API extends \JKingWeb\Arsse\REST\AbstractHandler {
     const LEVEL = 14;
     const VERSION = "17.4";
@@ -143,20 +156,126 @@ class API extends \JKingWeb\Arsse\REST\AbstractHandler {
             return Arsse::$db->folderAdd(Arsse::$user->id, $in);
         } catch (ExceptionInput $e) {
             switch ($e->getCode()) {
-                // folder already exists
-                case 10236:
-                    // retrieve the ID of the existing folder; duplicating a category silently returns the existing one
+                case 10236: // folder already exists
+                    // retrieve the ID of the existing folder; duplicating a folder silently returns the existing one
                     $folders = Arsse::$db->folderList(Arsse::$user->id, $in['parent'], false);
                     foreach ($folders as $folder) {
                         if ($folder['name']==$in['name']) {
                             return (int) $folder['id'];
                         }
                     }
-                // parent folder does not exist; this returns false as an ID
-                case 10235: return false;
-                // other errors related to input
-                default: throw new Exception("INCORRECT_USAGE");
+                    return false;
+                case 10235: // parent folder does not exist; this returns false as an ID
+                    return false;
+                default: // other errors related to input
+                    throw new Exception("INCORRECT_USAGE");
             }
         }
     }
+
+    public function opRemoveCategory(array $data) {
+        if (!isset($data['category_id']) || !ValueInfo::id($data['category_id'])) {
+            // if the folder is invalid, throw an error
+            throw new Exception("INCORRECT_USAGE");
+        }
+        try {
+            // attempt to remove the folder
+            Arsse::$db->folderRemove(Arsse::$user->id, (int) $data['category_id']);
+        } catch(ExceptionInput $e) {
+            // ignore all errors
+        }
+        return null;
+    }
+
+    public function opMoveCategory(array $data) {
+        if (!isset($data['category_id']) || !ValueInfo::id($data['category_id']) || !isset($data['parent_id']) || !ValueInfo::id($data['parent_id'], true)) {
+            // if the folder or parent is invalid, throw an error
+            throw new Exception("INCORRECT_USAGE");
+        }
+        $in = [
+            'parent' => (int) $data['parent_id'],
+        ];
+        try {
+            // try to move the folder
+            Arsse::$db->folderPropertiesSet(Arsse::$user->id, (int) $data['category_id'], $in);
+        } catch(ExceptionInput $e) {
+            // ignore all errors
+        }
+        return null;
+    }
+
+    public function opRenameCategory(array $data) {
+        if (!isset($data['category_id']) || !ValueInfo::id($data['category_id']) || !isset($data['caption'])) {
+            // if the folder is invalid, throw an error
+            throw new Exception("INCORRECT_USAGE");
+        }
+        $info = ValueInfo::str($data['caption']);
+        if (!($info & ValueInfo::VALID) || ($info & ValueInfo::EMPTY) || ($info & ValueInfo::WHITE)) {
+            // if the folder name is invalid, throw an error
+            throw new Exception("INCORRECT_USAGE");
+        }
+        $in = [
+            'name' => (string) $data['caption'],
+        ];
+        try {
+            // try to rename the folder
+            Arsse::$db->folderPropertiesSet(Arsse::$user->id, (int) $data['category_id'], $in);
+        } catch(ExceptionInput $e) {
+            // ignore all errors
+        }
+        return null;
+    }
+
+    public function opUnsubscribeFeed(array $data): array {
+        if (!isset($data['feed_id']) || !ValueInfo::id($data['feed_id'])) {
+            // if the feed is invalid, throw an error
+            throw new Exception("FEED_NOT_FOUND");
+        }
+        try {
+            // attempt to remove the feed
+            Arsse::$db->subscriptionRemove(Arsse::$user->id, (int) $data['feed_id']);
+        } catch(ExceptionInput $e) {
+            throw new Exception("FEED_NOT_FOUND");
+        }
+        return ['status' => "OK"];
+    }
+
+    public function opMoveFeed(array $data) {
+        if (!isset($data['feed_id']) || !ValueInfo::id($data['feed_id']) || !isset($data['category_id']) || !ValueInfo::id($data['category_id'], true)) {
+            // if the feed or folder is invalid, throw an error
+            throw new Exception("INCORRECT_USAGE");
+        }
+        $in = [
+            'folder' => (int) $data['category_id'],
+        ];
+        try {
+            // try to move the feed
+            Arsse::$db->subscriptionPropertiesSet(Arsse::$user->id, (int) $data['feed_id'], $in);
+        } catch(ExceptionInput $e) {
+            // ignore all errors
+        }
+        return null;
+    }
+
+    public function opRenameFeed(array $data) {
+        if (!isset($data['feed_id']) || !ValueInfo::id($data['feed_id']) || !isset($data['caption'])) {
+            // if the feed is invalid, throw an error
+            throw new Exception("INCORRECT_USAGE");
+        }
+        $info = ValueInfo::str($data['caption']);
+        if (!($info & ValueInfo::VALID) || ($info & ValueInfo::EMPTY) || ($info & ValueInfo::WHITE)) {
+            // if the feed name is invalid, throw an error
+            throw new Exception("INCORRECT_USAGE");
+        }
+        $in = [
+            'name' => (string) $data['caption'],
+        ];
+        try {
+            // try to rename the feed
+            Arsse::$db->subscriptionPropertiesSet(Arsse::$user->id, (int) $data['feed_id'], $in);
+        } catch(ExceptionInput $e) {
+            // ignore all errors
+        }
+        return null;
+    }
 }
diff --git a/tests/REST/TinyTinyRSS/TestTinyTinyAPI.php b/tests/REST/TinyTinyRSS/TestTinyTinyAPI.php
index a712b135..37aa594c 100644
--- a/tests/REST/TinyTinyRSS/TestTinyTinyAPI.php
+++ b/tests/REST/TinyTinyRSS/TestTinyTinyAPI.php
@@ -293,4 +293,212 @@ class TestTinyTinyAPI extends Test\AbstractTest {
         $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[3]))));
         $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[4]))));
     }
+
+    public function testRemoveACategory() {
+        $in = [
+            ['op' => "removeCategory", 'sid' => "PriestsOfSyrinx", 'category_id' => 42],
+            ['op' => "removeCategory", 'sid' => "PriestsOfSyrinx", 'category_id' => 2112],
+            ['op' => "removeCategory", 'sid' => "PriestsOfSyrinx", 'category_id' => -1],
+        ];
+        Phake::when(Arsse::$db)->folderRemove(Arsse::$user->id, $this->anything())->thenThrow(new ExceptionInput("subjectMissing"));
+        Phake::when(Arsse::$db)->folderRemove(Arsse::$user->id, 42)->thenReturn(true)->thenThrow(new ExceptionInput("subjectMissing"));
+        // succefully delete a folder
+        $exp = $this->respGood();
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[0]))));
+        // try deleting it again (this should silently fail)
+        $exp = $this->respGood();
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[0]))));
+        // delete a folder which does not exist (this should also silently fail)
+        $exp = $this->respGood();
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[1]))));
+        // delete an invalid folder (causes an error)
+        $exp = $this->respErr("INCORRECT_USAGE");
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[2]))));
+        Phake::verify(Arsse::$db, Phake::times(3))->folderRemove(Arsse::$user->id, $this->anything());
+    }
+
+    public function testMoveACategory() {
+        $in = [
+            ['op' => "moveCategory", 'sid' => "PriestsOfSyrinx", 'category_id' => 42, 'parent_id' => 1],
+            ['op' => "moveCategory", 'sid' => "PriestsOfSyrinx", 'category_id' => 2112, 'parent_id' => 2],
+            ['op' => "moveCategory", 'sid' => "PriestsOfSyrinx", 'category_id' => 42, 'parent_id' => 0],
+            ['op' => "moveCategory", 'sid' => "PriestsOfSyrinx", 'category_id' => 42, 'parent_id' => 47],
+            ['op' => "moveCategory", 'sid' => "PriestsOfSyrinx", 'category_id' => -1, 'parent_id' => 1],
+            ['op' => "moveCategory", 'sid' => "PriestsOfSyrinx", 'category_id' => 42, 'parent_id' => -1],
+            ['op' => "moveCategory", 'sid' => "PriestsOfSyrinx", 'category_id' => 42],
+            ['op' => "moveCategory", 'sid' => "PriestsOfSyrinx", 'parent_id' => -1],
+            ['op' => "moveCategory", 'sid' => "PriestsOfSyrinx"],
+        ];
+        $db = [
+            [Arsse::$user->id, 42, ['parent' => 1]],
+            [Arsse::$user->id, 2112, ['parent' => 2]],
+            [Arsse::$user->id, 42, ['parent' => 0]],
+            [Arsse::$user->id, 42, ['parent' => 47]],
+        ];
+        Phake::when(Arsse::$db)->folderPropertiesSet(...$db[0])->thenReturn(true);
+        Phake::when(Arsse::$db)->folderPropertiesSet(...$db[1])->thenThrow(new ExceptionInput("subjectMissing"));
+        Phake::when(Arsse::$db)->folderPropertiesSet(...$db[2])->thenThrow(new ExceptionInput("constraintViolation"));
+        Phake::when(Arsse::$db)->folderPropertiesSet(...$db[3])->thenThrow(new ExceptionInput("idMissing"));
+        // succefully move a folder
+        $exp = $this->respGood();
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[0]))));
+        // move a folder which does not exist (this should silently fail)
+        $exp = $this->respGood();
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[1]))));
+        // move a folder causing a duplication (this should also silently fail)
+        $exp = $this->respGood();
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[2]))));
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[3]))));
+        // all the rest should cause errors
+        $exp = $this->respErr("INCORRECT_USAGE");
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[4]))));
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[5]))));
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[6]))));
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[7]))));
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[8]))));
+        Phake::verify(Arsse::$db, Phake::times(4))->folderPropertiesSet(Arsse::$user->id, $this->anything(), $this->anything());
+    }
+
+    public function testRenameACategory() {
+        $in = [
+            ['op' => "renameCategory", 'sid' => "PriestsOfSyrinx", 'category_id' => 42, 'caption' => "Ook"],
+            ['op' => "renameCategory", 'sid' => "PriestsOfSyrinx", 'category_id' => 2112, 'caption' => "Eek"],
+            ['op' => "renameCategory", 'sid' => "PriestsOfSyrinx", 'category_id' => 42, 'caption' => "Eek"],
+            ['op' => "renameCategory", 'sid' => "PriestsOfSyrinx", 'category_id' => 42, 'caption' => ""],
+            ['op' => "renameCategory", 'sid' => "PriestsOfSyrinx", 'category_id' => 42, 'caption' => " "],
+            ['op' => "renameCategory", 'sid' => "PriestsOfSyrinx", 'category_id' => -1, 'caption' => "Ook"],
+            ['op' => "renameCategory", 'sid' => "PriestsOfSyrinx", 'category_id' => 42],
+            ['op' => "renameCategory", 'sid' => "PriestsOfSyrinx", 'caption' => "Ook"],
+            ['op' => "renameCategory", 'sid' => "PriestsOfSyrinx"],
+        ];
+        $db = [
+            [Arsse::$user->id, 42, ['name' => "Ook"]],
+            [Arsse::$user->id, 2112, ['name' => "Eek"]],
+            [Arsse::$user->id, 42, ['name' => "Eek"]],
+        ];
+        Phake::when(Arsse::$db)->folderPropertiesSet(...$db[0])->thenReturn(true);
+        Phake::when(Arsse::$db)->folderPropertiesSet(...$db[1])->thenThrow(new ExceptionInput("subjectMissing"));
+        Phake::when(Arsse::$db)->folderPropertiesSet(...$db[2])->thenThrow(new ExceptionInput("constraintViolation"));
+        // succefully rename a folder
+        $exp = $this->respGood();
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[0]))));
+        // rename a folder which does not exist (this should silently fail)
+        $exp = $this->respGood();
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[1]))));
+        // rename a folder causing a duplication (this should also silently fail)
+        $exp = $this->respGood();
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[2]))));
+        // all the rest should cause errors
+        $exp = $this->respErr("INCORRECT_USAGE");
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[3]))));
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[4]))));
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[5]))));
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[6]))));
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[7]))));
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[8]))));
+        Phake::verify(Arsse::$db, Phake::times(3))->folderPropertiesSet(Arsse::$user->id, $this->anything(), $this->anything());
+    }
+
+    public function testRemoveASubscription() {
+        $in = [
+            ['op' => "unsubscribeFeed", 'sid' => "PriestsOfSyrinx", 'feed_id' => 42],
+            ['op' => "unsubscribeFeed", 'sid' => "PriestsOfSyrinx", 'feed_id' => 2112],
+            ['op' => "unsubscribeFeed", 'sid' => "PriestsOfSyrinx", 'feed_id' => -1],
+            ['op' => "unsubscribeFeed", 'sid' => "PriestsOfSyrinx"],
+        ];
+        Phake::when(Arsse::$db)->subscriptionRemove(Arsse::$user->id, $this->anything())->thenThrow(new ExceptionInput("subjectMissing"));
+        Phake::when(Arsse::$db)->subscriptionRemove(Arsse::$user->id, 42)->thenReturn(true)->thenThrow(new ExceptionInput("subjectMissing"));
+        // succefully delete a folder
+        $exp = $this->respGood(['status' => "OK"]);
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[0]))));
+        // try deleting it again (this should noisily fail, as should everything else)
+        $exp = $this->respErr("FEED_NOT_FOUND");
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[0]))));
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[1]))));
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[2]))));
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[3]))));
+        Phake::verify(Arsse::$db, Phake::times(3))->subscriptionRemove(Arsse::$user->id, $this->anything());
+    }
+
+    public function testMoveASubscription() {
+        $in = [
+            ['op' => "moveFeed", 'sid' => "PriestsOfSyrinx", 'feed_id' => 42, 'category_id' => 1],
+            ['op' => "moveFeed", 'sid' => "PriestsOfSyrinx", 'feed_id' => 2112, 'category_id' => 2],
+            ['op' => "moveFeed", 'sid' => "PriestsOfSyrinx", 'feed_id' => 42, 'category_id' => 0],
+            ['op' => "moveFeed", 'sid' => "PriestsOfSyrinx", 'feed_id' => 42, 'category_id' => 47],
+            ['op' => "moveFeed", 'sid' => "PriestsOfSyrinx", 'feed_id' => -1, 'category_id' => 1],
+            ['op' => "moveFeed", 'sid' => "PriestsOfSyrinx", 'feed_id' => 42, 'category_id' => -1],
+            ['op' => "moveFeed", 'sid' => "PriestsOfSyrinx", 'feed_id' => 42],
+            ['op' => "moveFeed", 'sid' => "PriestsOfSyrinx", 'category_id' => -1],
+            ['op' => "moveFeed", 'sid' => "PriestsOfSyrinx"],
+        ];
+        $db = [
+            [Arsse::$user->id, 42, ['folder' => 1]],
+            [Arsse::$user->id, 2112, ['folder' => 2]],
+            [Arsse::$user->id, 42, ['folder' => 0]],
+            [Arsse::$user->id, 42, ['folder' => 47]],
+        ];
+        Phake::when(Arsse::$db)->subscriptionPropertiesSet(...$db[0])->thenReturn(true);
+        Phake::when(Arsse::$db)->subscriptionPropertiesSet(...$db[1])->thenThrow(new ExceptionInput("subjectMissing"));
+        Phake::when(Arsse::$db)->subscriptionPropertiesSet(...$db[2])->thenThrow(new ExceptionInput("constraintViolation"));
+        Phake::when(Arsse::$db)->subscriptionPropertiesSet(...$db[3])->thenThrow(new ExceptionInput("constraintViolation"));
+        // succefully move a subscription
+        $exp = $this->respGood();
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[0]))));
+        // move a subscription which does not exist (this should silently fail)
+        $exp = $this->respGood();
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[1]))));
+        // move a subscription causing a duplication (this should also silently fail)
+        $exp = $this->respGood();
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[2]))));
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[3]))));
+        // all the rest should cause errors
+        $exp = $this->respErr("INCORRECT_USAGE");
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[4]))));
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[5]))));
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[6]))));
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[7]))));
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[8]))));
+        Phake::verify(Arsse::$db, Phake::times(4))->subscriptionPropertiesSet(Arsse::$user->id, $this->anything(), $this->anything());
+    }
+
+    public function testRenameASubscription() {
+        $in = [
+            ['op' => "renameFeed", 'sid' => "PriestsOfSyrinx", 'feed_id' => 42, 'caption' => "Ook"],
+            ['op' => "renameFeed", 'sid' => "PriestsOfSyrinx", 'feed_id' => 2112, 'caption' => "Eek"],
+            ['op' => "renameFeed", 'sid' => "PriestsOfSyrinx", 'feed_id' => 42, 'caption' => "Eek"],
+            ['op' => "renameFeed", 'sid' => "PriestsOfSyrinx", 'feed_id' => 42, 'caption' => ""],
+            ['op' => "renameFeed", 'sid' => "PriestsOfSyrinx", 'feed_id' => 42, 'caption' => " "],
+            ['op' => "renameFeed", 'sid' => "PriestsOfSyrinx", 'feed_id' => -1, 'caption' => "Ook"],
+            ['op' => "renameFeed", 'sid' => "PriestsOfSyrinx", 'feed_id' => 42],
+            ['op' => "renameFeed", 'sid' => "PriestsOfSyrinx", 'caption' => "Ook"],
+            ['op' => "renameFeed", 'sid' => "PriestsOfSyrinx"],
+        ];
+        $db = [
+            [Arsse::$user->id, 42, ['name' => "Ook"]],
+            [Arsse::$user->id, 2112, ['name' => "Eek"]],
+            [Arsse::$user->id, 42, ['name' => "Eek"]],
+        ];
+        Phake::when(Arsse::$db)->subscriptionPropertiesSet(...$db[0])->thenReturn(true);
+        Phake::when(Arsse::$db)->subscriptionPropertiesSet(...$db[1])->thenThrow(new ExceptionInput("subjectMissing"));
+        Phake::when(Arsse::$db)->subscriptionPropertiesSet(...$db[2])->thenThrow(new ExceptionInput("constraintViolation"));
+        // succefully rename a subscription
+        $exp = $this->respGood();
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[0]))));
+        // rename a subscription which does not exist (this should silently fail)
+        $exp = $this->respGood();
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[1]))));
+        // rename a subscription causing a duplication (this should also silently fail)
+        $exp = $this->respGood();
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[2]))));
+        // all the rest should cause errors
+        $exp = $this->respErr("INCORRECT_USAGE");
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[3]))));
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[4]))));
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[5]))));
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[6]))));
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[7]))));
+        $this->assertEquals($exp, $this->h->dispatch(new Request("POST", "", json_encode($in[8]))));
+        Phake::verify(Arsse::$db, Phake::times(3))->subscriptionPropertiesSet(Arsse::$user->id, $this->anything(), $this->anything());
+    }
 }