diff --git a/Userland/Games/Chess/ChessWidget.cpp b/Userland/Games/Chess/ChessWidget.cpp
index d736c5fbfe..0185c5b54a 100644
--- a/Userland/Games/Chess/ChessWidget.cpp
+++ b/Userland/Games/Chess/ChessWidget.cpp
@@ -535,7 +535,7 @@ void ChessWidget::playback_move(PlaybackDirection direction)
 
 DeprecatedString ChessWidget::get_fen() const
 {
-    return m_playback ? m_board_playback.to_fen() : m_board.to_fen();
+    return (m_playback ? m_board_playback.to_fen() : m_board.to_fen()).release_value_but_fixme_should_propagate_errors().to_deprecated_string();
 }
 
 ErrorOr<void> ChessWidget::import_pgn(Core::File& file)
@@ -659,10 +659,10 @@ ErrorOr<void> ChessWidget::export_pgn(Core::File& file) const
 
     // Movetext Section
     for (size_t i = 0, move_no = 1; i < m_board.moves().size(); i += 2, move_no++) {
-        const DeprecatedString white = m_board.moves().at(i).to_algebraic();
+        const DeprecatedString white = m_board.moves().at(i).to_algebraic().release_value_but_fixme_should_propagate_errors().to_deprecated_string();
 
         if (i + 1 < m_board.moves().size()) {
-            const DeprecatedString black = m_board.moves().at(i + 1).to_algebraic();
+            const DeprecatedString black = m_board.moves().at(i + 1).to_algebraic().release_value_but_fixme_should_propagate_errors().to_deprecated_string();
             TRY(file.write_until_depleted(DeprecatedString::formatted("{}. {} {} ", move_no, white, black).bytes()));
         } else {
             TRY(file.write_until_depleted(DeprecatedString::formatted("{}. {} ", move_no, white).bytes()));
diff --git a/Userland/Libraries/LibChess/Chess.cpp b/Userland/Libraries/LibChess/Chess.cpp
index cf8d24ee05..ca491cb259 100644
--- a/Userland/Libraries/LibChess/Chess.cpp
+++ b/Userland/Libraries/LibChess/Chess.cpp
@@ -7,7 +7,7 @@
 
 #include <AK/Assertions.h>
 #include <AK/CharacterTypes.h>
-#include <AK/DeprecatedString.h>
+#include <AK/String.h>
 #include <AK/StringBuilder.h>
 #include <AK/Vector.h>
 #include <LibChess/Chess.h>
@@ -94,12 +94,9 @@ char Square::rank_char() const
     return rank + '1';
 }
 
-DeprecatedString Square::to_algebraic() const
+ErrorOr<String> Square::to_algebraic() const
 {
-    StringBuilder builder;
-    builder.append(file + 'a');
-    builder.append(rank + '1');
-    return builder.to_deprecated_string();
+    return String::formatted("{}{}", file_char(), rank_char());
 }
 
 Move::Move(StringView long_algebraic)
@@ -109,14 +106,14 @@ Move::Move(StringView long_algebraic)
 {
 }
 
-DeprecatedString Move::to_long_algebraic() const
+ErrorOr<String> Move::to_long_algebraic() const
 {
     StringBuilder builder;
-    builder.append(from.to_algebraic());
-    builder.append(to.to_algebraic());
+    TRY(builder.try_append(TRY(from.to_algebraic())));
+    TRY(builder.try_append(TRY(to.to_algebraic())));
     if (auto promoted_char = char_for_piece(promote_to, Notation::Algebraic); promoted_char.has_value())
-        builder.append(to_ascii_lowercase(promoted_char.value()));
-    return builder.to_deprecated_string();
+        TRY(builder.try_append(to_ascii_lowercase(promoted_char.value())));
+    return builder.to_string();
 }
 
 Move Move::from_algebraic(StringView algebraic, const Color turn, Board const& board)
@@ -195,48 +192,48 @@ Move Move::from_algebraic(StringView algebraic, const Color turn, Board const& b
     return move;
 }
 
-DeprecatedString Move::to_algebraic() const
+ErrorOr<String> Move::to_algebraic() const
 {
     if (piece.type == Type::King && from.file == 4) {
         if (to.file == 2)
-            return "O-O-O";
+            return "O-O-O"_short_string;
         if (to.file == 6)
-            return "O-O";
+            return "O-O"_short_string;
     }
 
     StringBuilder builder;
 
     if (auto piece_char = char_for_piece(piece.type, Notation::Algebraic); piece_char.has_value())
-        builder.append(*piece_char);
+        TRY(builder.try_append(*piece_char));
 
     if (is_ambiguous) {
         if (from.file != ambiguous.file)
-            builder.append(from.file_char());
+            TRY(builder.try_append(from.file_char()));
         else if (from.rank != ambiguous.rank)
-            builder.append(from.rank_char());
+            TRY(builder.try_append(from.rank_char()));
         else
-            builder.append(from.to_algebraic());
+            TRY(builder.try_append(TRY(from.to_algebraic())));
     }
 
     if (is_capture) {
         if (piece.type == Type::Pawn && !is_ambiguous)
-            builder.append(from.file_char());
-        builder.append('x');
+            TRY(builder.try_append(from.file_char()));
+        TRY(builder.try_append('x'));
     }
 
-    builder.append(to.to_algebraic());
+    TRY(builder.try_append(TRY(to.to_algebraic())));
 
     if (promote_to != Type::None && promote_to != Type::Pawn) {
-        builder.append('=');
-        builder.append(char_for_piece(promote_to, Notation::Algebraic).value());
+        TRY(builder.try_append('='));
+        TRY(builder.try_append(char_for_piece(promote_to, Notation::Algebraic).value()));
     }
 
     if (is_mate)
-        builder.append('#');
+        TRY(builder.try_append('#'));
     else if (is_check)
-        builder.append('+');
+        TRY(builder.try_append('+'));
 
-    return builder.to_deprecated_string();
+    return builder.to_string();
 }
 
 Board::Board()
@@ -289,7 +286,7 @@ Board Board::clone_without_history() const
     return result;
 }
 
-DeprecatedString Board::to_fen() const
+ErrorOr<String> Board::to_fen() const
 {
     StringBuilder builder;
 
@@ -303,57 +300,61 @@ DeprecatedString Board::to_fen() const
                 continue;
             }
             if (empty > 0) {
-                builder.append(DeprecatedString::number(empty));
+                TRY(builder.try_appendff("{}", empty));
                 empty = 0;
             }
             auto const piece = char_for_piece(p.type, Notation::FEN).value();
             if (p.color == Color::Black)
-                builder.append(to_ascii_lowercase(piece));
+                TRY(builder.try_append(to_ascii_lowercase(piece)));
             else
-                builder.append(piece);
+                TRY(builder.try_append(piece));
         }
         if (empty > 0) {
-            builder.append(DeprecatedString::number(empty));
+            TRY(builder.try_appendff("{}", empty));
             empty = 0;
         }
         if (rank < 7)
-            builder.append('/');
+            TRY(builder.try_append('/'));
     }
 
     // 2. Active color
     VERIFY(m_turn != Color::None);
-    builder.append(m_turn == Color::White ? " w "sv : " b "sv);
+    TRY(builder.try_append(m_turn == Color::White ? " w "sv : " b "sv));
 
     // 3. Castling availability
-    builder.append(m_white_can_castle_kingside ? "K"sv : ""sv);
-    builder.append(m_white_can_castle_queenside ? "Q"sv : ""sv);
-    builder.append(m_black_can_castle_kingside ? "k"sv : ""sv);
-    builder.append(m_black_can_castle_queenside ? "q"sv : ""sv);
-    builder.append(' ');
+    if (m_white_can_castle_kingside)
+        TRY(builder.try_append('K'));
+    if (m_white_can_castle_queenside)
+        TRY(builder.try_append('Q'));
+    if (m_black_can_castle_kingside)
+        TRY(builder.try_append('k'));
+    if (m_black_can_castle_queenside)
+        TRY(builder.try_append('q'));
+    TRY(builder.try_append(' '));
 
     // 4. En passant target square
     if (!m_last_move.has_value())
-        builder.append('-');
+        TRY(builder.try_append('-'));
     else if (m_last_move.value().piece.type == Type::Pawn) {
         if (m_last_move.value().from.rank == 1 && m_last_move.value().to.rank == 3)
-            builder.append(Square(m_last_move.value().to.rank - 1, m_last_move.value().to.file).to_algebraic());
+            TRY(builder.try_append(TRY(Square(m_last_move.value().to.rank - 1, m_last_move.value().to.file).to_algebraic())));
         else if (m_last_move.value().from.rank == 6 && m_last_move.value().to.rank == 4)
-            builder.append(Square(m_last_move.value().to.rank + 1, m_last_move.value().to.file).to_algebraic());
+            TRY(builder.try_append(TRY(Square(m_last_move.value().to.rank + 1, m_last_move.value().to.file).to_algebraic())));
         else
-            builder.append('-');
+            TRY(builder.try_append('-'));
     } else {
-        builder.append('-');
+        TRY(builder.try_append('-'));
     }
-    builder.append(' ');
+    TRY(builder.try_append(' '));
 
     // 5. Halfmove clock
-    builder.append(DeprecatedString::number(min(m_moves_since_capture, m_moves_since_pawn_advance)));
-    builder.append(' ');
+    TRY(builder.try_appendff("{}", (min(m_moves_since_capture, m_moves_since_pawn_advance))));
+    TRY(builder.try_append(' '));
 
     // 6. Fullmove number
-    builder.append(DeprecatedString::number(1 + m_moves.size() / 2));
+    TRY(builder.try_appendff("{}", (1 + m_moves.size() / 2)));
 
-    return builder.to_deprecated_string();
+    return builder.to_string();
 }
 
 Piece Board::get_piece(Square const& square) const
diff --git a/Userland/Libraries/LibChess/Chess.h b/Userland/Libraries/LibChess/Chess.h
index 554eda0fe3..acff4ee9d4 100644
--- a/Userland/Libraries/LibChess/Chess.h
+++ b/Userland/Libraries/LibChess/Chess.h
@@ -93,7 +93,7 @@ struct Square {
 
     char file_char() const;
     char rank_char() const;
-    DeprecatedString to_algebraic() const;
+    ErrorOr<String> to_algebraic() const;
 };
 
 class Board;
@@ -118,8 +118,8 @@ struct Move {
     bool operator==(Move const& other) const { return from == other.from && to == other.to && promote_to == other.promote_to; }
 
     static Move from_algebraic(StringView algebraic, const Color turn, Board const& board);
-    DeprecatedString to_long_algebraic() const;
-    DeprecatedString to_algebraic() const;
+    ErrorOr<String> to_long_algebraic() const;
+    ErrorOr<String> to_algebraic() const;
 };
 
 class Board {
@@ -138,7 +138,7 @@ public:
     bool apply_move(Move const&, Color color = Color::None);
     Optional<Move> const& last_move() const { return m_last_move; }
 
-    DeprecatedString to_fen() const;
+    ErrorOr<String> to_fen() const;
 
     enum class Result {
         CheckMate,
diff --git a/Userland/Libraries/LibChess/UCICommand.cpp b/Userland/Libraries/LibChess/UCICommand.cpp
index a97c110097..d83aa08864 100644
--- a/Userland/Libraries/LibChess/UCICommand.cpp
+++ b/Userland/Libraries/LibChess/UCICommand.cpp
@@ -141,7 +141,7 @@ ErrorOr<String> PositionCommand::to_string() const
     TRY(builder.try_append("moves"sv));
     for (auto& move : moves()) {
         TRY(builder.try_append(' '));
-        TRY(builder.try_append(move.to_long_algebraic()));
+        TRY(builder.try_append(TRY(move.to_long_algebraic())));
     }
     TRY(builder.try_append('\n'));
     return builder.to_string();
@@ -202,7 +202,7 @@ ErrorOr<String> GoCommand::to_string() const
         TRY(builder.try_append(" searchmoves"sv));
         for (auto& move : searchmoves.value()) {
             TRY(builder.try_append(' '));
-            TRY(builder.try_append(move.to_long_algebraic()));
+            TRY(builder.try_append(TRY(move.to_long_algebraic())));
         }
     }
 
@@ -318,7 +318,7 @@ ErrorOr<String> BestMoveCommand::to_string() const
 {
     StringBuilder builder;
     TRY(builder.try_append("bestmove "sv));
-    TRY(builder.try_append(move().to_long_algebraic()));
+    TRY(builder.try_append(TRY(move().to_long_algebraic())));
     TRY(builder.try_append('\n'));
     return builder.to_string();
 }