diff --git a/cpp/src/monoformat_parsehelpers.hpp b/cpp/src/monoformat_parsehelpers.hpp
index 503159c..9e2ca4c 100644
--- a/cpp/src/monoformat_parsehelpers.hpp
+++ b/cpp/src/monoformat_parsehelpers.hpp
@@ -5,6 +5,7 @@
 #include <cstddef>
 #include <expected>
 #include <span>
+#include <tuple> // for std::ignore
 
 namespace monoformat {
 
@@ -228,6 +229,125 @@ inline std::pair<std::uint8_t, bool> overflowingShl(std::uint8_t value, std::uin
     return {value << bits, overflow};
 }
 
+inline std::size_t writeU8LE(std::span<std::byte>& target, std::size_t pos, std::uint8_t value) {
+    if (pos < target.size()) {
+        target[pos] = static_cast<std::byte>(value);
+    }
+    return pos + 1;
+}
+
+inline std::size_t writeU8BE(std::span<std::byte>& target, std::size_t pos, std::uint8_t value) {
+    if (pos < target.size()) {
+        target[pos] = static_cast<std::byte>(value);
+    }
+    return pos + 1;
+}
+
+inline std::size_t writeU16LE(std::span<std::byte>& target, std::size_t pos, std::uint16_t value) {
+    if ((pos + 1) < target.size()) {
+        target[pos + 0] = static_cast<std::byte>((value >> 0u) & 0xffu);
+        target[pos + 1] = static_cast<std::byte>((value >> 8u) & 0xffu);
+    }
+    return pos + 2;
+}
+
+inline std::size_t writeU16BE(std::span<std::byte>& target, std::size_t pos, std::uint16_t value) {
+    if ((pos + 1) < target.size()) {
+        target[pos + 0] = static_cast<std::byte>((value >> 8u) & 0xffu);
+        target[pos + 1] = static_cast<std::byte>((value >> 0u) & 0xffu);
+    }
+    return pos + 2;
+}
+
+inline std::size_t writeU24LE(std::span<std::byte>& target, std::size_t pos, std::uint32_t value) {
+    if ((pos + 2) < target.size()) {
+        target[pos + 0] = static_cast<std::byte>((value >> 0u) & 0xffu);
+        target[pos + 1] = static_cast<std::byte>((value >> 8u) & 0xffu);
+        target[pos + 2] = static_cast<std::byte>((value >> 16u) & 0xffu);
+    }
+    return pos + 3;
+}
+
+inline std::size_t writeU24BE(std::span<std::byte>& target, std::size_t pos, std::uint32_t value) {
+    if ((pos + 2) < target.size()) {
+        target[pos + 0] = static_cast<std::byte>((value >> 16u) & 0xffu);
+        target[pos + 1] = static_cast<std::byte>((value >> 8u) & 0xffu);
+        target[pos + 2] = static_cast<std::byte>((value >> 0u) & 0xffu);
+    }
+    return pos + 3;
+}
+
+inline std::size_t writeU32LE(std::span<std::byte>& target, std::size_t pos, std::uint32_t value) {
+    if ((pos + 3) < target.size()) {
+        target[pos + 0] = static_cast<std::byte>((value >> 0u) & 0xffu);
+        target[pos + 1] = static_cast<std::byte>((value >> 8u) & 0xffu);
+        target[pos + 2] = static_cast<std::byte>((value >> 16u) & 0xffu);
+        target[pos + 3] = static_cast<std::byte>((value >> 24u) & 0xffu);
+    }
+    return pos + 4;
+}
+
+inline std::size_t writeU32BE(std::span<std::byte>& target, std::size_t pos, std::uint32_t value) {
+    if ((pos + 3) < target.size()) {
+        target[pos + 0] = static_cast<std::byte>((value >> 24u) & 0xffu);
+        target[pos + 1] = static_cast<std::byte>((value >> 16u) & 0xffu);
+        target[pos + 2] = static_cast<std::byte>((value >> 8u) & 0xffu);
+        target[pos + 3] = static_cast<std::byte>((value >> 0u) & 0xffu);
+    }
+    return pos + 4;
+}
+
+inline std::size_t writeU64LE(std::span<std::byte>& target, std::size_t pos, std::uint64_t value) {
+    if ((pos + 7) < target.size()) {
+        target[pos + 0] = static_cast<std::byte>((value >> 0u) & 0xffu);
+        target[pos + 1] = static_cast<std::byte>((value >> 8u) & 0xffu);
+        target[pos + 2] = static_cast<std::byte>((value >> 16u) & 0xffu);
+        target[pos + 3] = static_cast<std::byte>((value >> 24u) & 0xffu);
+        target[pos + 4] = static_cast<std::byte>((value >> 32u) & 0xffu);
+        target[pos + 5] = static_cast<std::byte>((value >> 40u) & 0xffu);
+        target[pos + 6] = static_cast<std::byte>((value >> 48u) & 0xffu);
+        target[pos + 7] = static_cast<std::byte>((value >> 56u) & 0xffu);
+    }
+    return pos + 8;
+}
+
+inline std::size_t writeU64BE(std::span<std::byte>& target, std::size_t pos, std::uint64_t value) {
+    if ((pos + 3) < target.size()) {
+        target[pos + 0] = static_cast<std::byte>((value >> 56u) & 0xffu);
+        target[pos + 1] = static_cast<std::byte>((value >> 48u) & 0xffu);
+        target[pos + 2] = static_cast<std::byte>((value >> 40u) & 0xffu);
+        target[pos + 3] = static_cast<std::byte>((value >> 32u) & 0xffu);
+        target[pos + 4] = static_cast<std::byte>((value >> 24u) & 0xffu);
+        target[pos + 5] = static_cast<std::byte>((value >> 16u) & 0xffu);
+        target[pos + 6] = static_cast<std::byte>((value >> 8u) & 0xffu);
+        target[pos + 7] = static_cast<std::byte>((value >> 0u) & 0xffu);
+    }
+    return pos + 8;
+}
+
+inline std::size_t writeBuffer(std::span<std::byte>& target, std::size_t pos, std::span<std::byte const> value) {
+    if ((pos + value.size()) > target.size()) {
+        if (pos < value.size()) {
+            std::size_t const n = value.size() - pos;
+            std::copy(value.begin(), value.begin() + n, target.begin() + pos);
+        }
+    } else {
+        std::copy(value.begin(), value.end(), target.begin() + pos);
+    }
+    return pos + value.size();
+}
+
+inline std::size_t alignNextWrite(std::span<std::byte>& target, std::size_t pos, std::size_t alignment) {
+    std::ignore = target;
+    if (alignment <= 1) {
+        return pos;
+    }
+    if (pos % alignment == 0) {
+        return pos;
+    }
+    return ((pos + alignment - 1) / alignment) * alignment;
+}
+
 } // namespace monoformat
 
 #endif // MONOFORMAT_PARSEHELPERS_HPP
diff --git a/cpp/src/monoformat_structured.cpp b/cpp/src/monoformat_structured.cpp
index 940d435..0ac5475 100644
--- a/cpp/src/monoformat_structured.cpp
+++ b/cpp/src/monoformat_structured.cpp
@@ -122,7 +122,15 @@ ElementType ImageElement::elementType() const {
 }
 
 std::size_t ImageElement::serializeTo(std::span<std::byte> target) const {
-    // FIXME: serialize
+    std::size_t pos = 0;
+    pos = writeU16LE(target, pos, static_cast<std::uint16_t>(ElementType::Image));
+    pos = writeU16LE(target, pos, m_x);
+    pos = writeU16LE(target, pos, m_y);
+    pos = writeU16LE(target, pos, m_width);
+    pos = writeU16LE(target, pos, m_height);
+    pos = writeU16LE(target, pos, 0);
+    pos = writeBuffer(target, pos, m_buffer);
+    return alignNextWrite(target, pos, 4);
 }
 
 void ImageElement::drawTo(OneBitBufferInterface* imageBuffer, std::size_t animationTick, std::int64_t currentTimestamp) {
@@ -209,7 +217,17 @@ ElementType AnimationElement::elementType() const {
 }
 
 std::size_t AnimationElement::serializeTo(std::span<std::byte> target) const {
-    // FIXME: implement this
+    std::size_t pos = 0;
+    pos = writeU16LE(target, pos, static_cast<std::uint16_t>(ElementType::Animation));
+    pos = writeU16LE(target, pos, m_x);
+    pos = writeU16LE(target, pos, m_y);
+    pos = writeU16LE(target, pos, m_width);
+    pos = writeU16LE(target, pos, m_height);
+    pos = writeU16LE(target, pos, m_numberOfFrames);
+    pos = writeU16LE(target, pos, m_updateInterval);
+    pos = writeU16LE(target, pos, 0);
+    pos = writeBuffer(target, pos, m_buffer);
+    return alignNextWrite(target, pos, 4);
 }
 
 void AnimationElement::drawTo(OneBitBufferInterface* imageBuffer, std::size_t animationTick, std::int64_t currentTimestamp) {
@@ -285,7 +303,18 @@ ElementType HScrollImageElement::elementType() const {
 }
 
 std::size_t HScrollImageElement::serializeTo(std::span<std::byte> target) const {
-    // FIXME Serialize
+    std::size_t pos = 0;
+    pos = writeU16LE(target, pos, static_cast<std::uint16_t>(ElementType::HScrollImage));
+    pos = writeU16LE(target, pos, m_x);
+    pos = writeU16LE(target, pos, m_y);
+    pos = writeU16LE(target, pos, m_width);
+    pos = writeU16LE(target, pos, m_height);
+    pos = writeU16LE(target, pos, m_contentWidth);
+    pos = writeU8LE(target, pos, m_flags);
+    pos = writeU8LE(target, pos, m_scrollSpeed);
+    pos = writeU16LE(target, pos, 0);
+    pos = writeBuffer(target, pos, m_buffer);
+    return alignNextWrite(target, pos, 4);
 }
 
 void HScrollImageElement::drawTo(OneBitBufferInterface* imageBuffer, std::size_t animationTick, std::int64_t currentTimestamp) {
@@ -361,7 +390,18 @@ ElementType VScrollImageElement::elementType() const {
 }
 
 std::size_t VScrollImageElement::serializeTo(std::span<std::byte> target) const {
-    // FIXME Serialize
+    std::size_t pos = 0;
+    pos = writeU16LE(target, pos, static_cast<std::uint16_t>(ElementType::VScrollImage));
+    pos = writeU16LE(target, pos, m_x);
+    pos = writeU16LE(target, pos, m_y);
+    pos = writeU16LE(target, pos, m_width);
+    pos = writeU16LE(target, pos, m_height);
+    pos = writeU16LE(target, pos, m_contentHeight);
+    pos = writeU8LE(target, pos, m_flags);
+    pos = writeU8LE(target, pos, m_scrollSpeed);
+    pos = writeU16LE(target, pos, 0);
+    pos = writeBuffer(target, pos, m_buffer);
+    return alignNextWrite(target, pos, 4);
 }
 
 void VScrollImageElement::drawTo(OneBitBufferInterface* imageBuffer, std::size_t animationTick, std::int64_t currentTimestamp) {
@@ -415,7 +455,15 @@ ElementType LineElement::elementType() const {
 }
 
 std::size_t LineElement::serializeTo(std::span<std::byte> target) const {
-    // FIXME: serialize
+    std::size_t pos = 0;
+    pos = writeU16LE(target, pos, static_cast<std::uint16_t>(ElementType::Line));
+    pos = writeU16LE(target, pos, m_originX);
+    pos = writeU16LE(target, pos, m_originY);
+    pos = writeU16LE(target, pos, m_targetX);
+    pos = writeU16LE(target, pos, m_targetY);
+    pos = writeU8LE(target, pos, static_cast<std::uint8_t>(m_lineStyle));
+    pos = writeU8LE(target, pos, m_flags);
+    return alignNextWrite(target, pos, 4);
 }
 
 void LineElement::drawTo(OneBitBufferInterface* imageBuffer, std::size_t animationTick, std::int64_t currentTimestamp) {
@@ -468,7 +516,16 @@ ElementType ClippedTextElement::elementType() const {
 }
 
 std::size_t ClippedTextElement::serializeTo(std::span<std::byte> target) const {
-    // FIXME: serialize
+    std::size_t pos = 0;
+    pos = writeU16LE(target, pos, static_cast<std::uint16_t>(ElementType::HScrollImage));
+    pos = writeU16LE(target, pos, m_x);
+    pos = writeU16LE(target, pos, m_y);
+    pos = writeU16LE(target, pos, m_width);
+    pos = writeU16LE(target, pos, m_height);
+    pos = writeU16LE(target, pos, m_fontIndex);
+    pos = writeU16LE(target, pos, m_text.size());
+    pos = writeBuffer(target, pos, std::as_bytes(std::span{m_text}));
+    return alignNextWrite(target, pos, 4);
 }
 
 void ClippedTextElement::drawTo(OneBitBufferInterface* imageBuffer, std::size_t animationTick, std::int64_t currentTimestamp) {
@@ -531,7 +588,18 @@ ElementType HScrollTextElement::elementType() const {
 }
 
 std::size_t HScrollTextElement::serializeTo(std::span<std::byte> target) const {
-    // FIXME serialize
+    std::size_t pos = 0;
+    pos = writeU16LE(target, pos, static_cast<std::uint16_t>(ElementType::HScrollImage));
+    pos = writeU16LE(target, pos, m_x);
+    pos = writeU16LE(target, pos, m_y);
+    pos = writeU16LE(target, pos, m_width);
+    pos = writeU16LE(target, pos, m_height);
+    pos = writeU8LE(target, pos, m_flags);
+    pos = writeU8LE(target, pos, m_scrollSpeed);
+    pos = writeU16LE(target, pos, m_fontIndex);
+    pos = writeU16LE(target, pos, m_text.size());
+    pos = writeBuffer(target, pos, std::as_bytes(std::span{m_text}));
+    return alignNextWrite(target, pos, 4);
 }
 
 void HScrollTextElement::drawTo(OneBitBufferInterface* imageBuffer, std::size_t animationTick, std::int64_t currentTimestamp) {
@@ -589,7 +657,16 @@ ElementType CurrentTimeElement::elementType() const {
 }
 
 std::size_t CurrentTimeElement::serializeTo(std::span<std::byte> target) const {
-    // FIXME: serialize
+    std::size_t pos = 0;
+    pos = writeU16LE(target, pos, static_cast<std::uint16_t>(ElementType::HScrollImage));
+    pos = writeU16LE(target, pos, m_x);
+    pos = writeU16LE(target, pos, m_y);
+    pos = writeU16LE(target, pos, m_width);
+    pos = writeU16LE(target, pos, m_height);
+    pos = writeU16LE(target, pos, m_fontIndex);
+    pos = writeU16LE(target, pos, m_utcOffset);
+    pos = writeU16LE(target, pos, m_flags);
+    return alignNextWrite(target, pos, 4);
 }
 
 void CurrentTimeElement::drawTo(OneBitBufferInterface* imageBuffer, std::size_t animationTick, std::int64_t currentTimestamp) {
@@ -674,7 +751,32 @@ SectionType AlwaysDrawnSection::sectionType() const {
 }
 
 std::size_t AlwaysDrawnSection::serializeTo(std::span<std::byte> target) const {
-    // FIXME: serialize
+    std::size_t pos = 0;
+    pos = writeU8LE(target, pos, static_cast<std::uint16_t>(SectionType::AlwaysDrawn));
+    // Will be replaced later
+    pos = writeU24LE(target, pos, 0);
+    std::uint16_t flags = 0;
+    if (m_drawOnFront) {
+        flags |= std::uint16_t{1};
+    }
+    if (m_drawOnBack) {
+        flags |= std::uint16_t{2};
+    }
+    if (m_clearBeforeDrawing) {
+        flags |= std::uint16_t{4};
+    }
+    pos = writeU16LE(target, pos, flags);
+    pos = writeU16LE(target, pos, m_elements.size());
+    for (auto const& element : m_elements) {
+        if (pos < target.size()) {
+            pos += element->serializeTo(target.subspan(pos));
+        } else {
+            pos += element->serializeTo({});
+        }
+    }
+    pos = alignNextWrite(target, pos, 4);
+    std::ignore = writeU24LE(target, 1, pos);
+    return pos;
 }
 
 std::expected<std::unique_ptr<AlwaysDrawnSection>, ParseError> AlwaysDrawnSection::parse(std::span<std::byte const>& buffer) {
@@ -771,7 +873,34 @@ SectionType TimeBasedDrawnSection::sectionType() const {
 }
 
 std::size_t TimeBasedDrawnSection::serializeTo(std::span<std::byte> target) const {
-    // FIXME: serialize
+    std::size_t pos = 0;
+    pos = writeU8LE(target, pos, static_cast<std::uint16_t>(SectionType::AlwaysDrawn));
+    // Will be replaced later
+    pos = writeU24LE(target, pos, 0);
+    std::uint16_t flags = 0;
+    if (m_drawOnFront) {
+        flags |= std::uint16_t{1};
+    }
+    if (m_drawOnBack) {
+        flags |= std::uint16_t{2};
+    }
+    if (m_clearBeforeDrawing) {
+        flags |= std::uint16_t{4};
+    }
+    pos = writeU16LE(target, pos, flags);
+    pos = writeU16LE(target, pos, m_elements.size());
+    pos = writeU64LE(target, pos, std::bit_cast<std::uint64_t>(m_startTimestamp));
+    pos = writeU64LE(target, pos, std::bit_cast<std::uint64_t>(m_endTimestamp));
+    for (auto const& element : m_elements) {
+        if (pos < target.size()) {
+            pos += element->serializeTo(target.subspan(pos));
+        } else {
+            pos += element->serializeTo({});
+        }
+    }
+    pos = alignNextWrite(target, pos, 4);
+    std::ignore = writeU24LE(target, 1, pos);
+    return pos;
 }
 
 std::expected<std::unique_ptr<TimeBasedDrawnSection>, ParseError> TimeBasedDrawnSection::parse(std::span<std::byte const>& buffer) {
@@ -795,7 +924,16 @@ SectionType CustomFontSection::sectionType() const {
 }
 
 std::size_t CustomFontSection::serializeTo(std::span<std::byte> target) const {
-    // FIXME: serailize
+    std::size_t pos = 0;
+    pos = writeU8LE(target, pos, static_cast<std::uint16_t>(SectionType::AlwaysDrawn));
+    // Will be replaced later
+    pos = writeU24LE(target, pos, 0);
+    pos = writeU24LE(target, pos, m_fontData.size());
+    pos = writeU8LE(target, pos, 0);
+    pos = writeBuffer(target, pos, m_fontData);
+    pos = alignNextWrite(target, pos, 4);
+    std::ignore = writeU24LE(target, 1, pos);
+    return pos;
 }
 
 std::expected<std::unique_ptr<CustomFontSection>, ParseError> CustomFontSection::parse(std::span<std::byte const>& buffer) {
@@ -803,7 +941,23 @@ std::expected<std::unique_ptr<CustomFontSection>, ParseError> CustomFontSection:
 }
 
 std::size_t serializeFile(std::span<std::byte>& buffer, File const& file) {
-    // FIXME: serialize
+    std::size_t pos = 0;
+    pos = writeU8LE(buffer, pos, 0xAF);
+    pos = writeU8LE(buffer, pos, 0x7E);
+    pos = writeU8LE(buffer, pos, 0x2B);
+    pos = writeU8LE(buffer, pos, 0x64);
+    pos = writeU32LE(buffer, pos, 1);
+    pos = writeU16LE(buffer, pos, file.sections.size());
+    pos = writeU16LE(buffer, pos, 0);
+    pos = alignNextWrite(buffer, pos, 4);
+    for (auto const& section : file.sections) {
+        if (pos < buffer.size()) {
+            pos += section->serializeTo(buffer.subspan(pos));
+        } else {
+            pos += section->serializeTo({});
+        }
+    }
+    return pos;
 }
 
 std::expected<File, ParseError> parseFile(std::span<std::byte const> data) {