diff --git a/ext/crates/sseq/src/charting/mod.rs b/ext/crates/sseq/src/charting/mod.rs
index 4dde744944..2b0d0821dc 100644
--- a/ext/crates/sseq/src/charting/mod.rs
+++ b/ext/crates/sseq/src/charting/mod.rs
@@ -2,9 +2,11 @@ use std::fmt::Display;
 
 use crate::coordinates::{Bidegree, BidegreeGenerator};
 
+pub mod seqsee;
 pub mod svg;
 pub mod tikz;
 
+pub use seqsee::SeqSeeBackend;
 pub use svg::SvgBackend;
 pub use tikz::TikzBackend;
 
diff --git a/ext/crates/sseq/src/charting/seqsee.rs b/ext/crates/sseq/src/charting/seqsee.rs
new file mode 100644
index 0000000000..6d530c296f
--- /dev/null
+++ b/ext/crates/sseq/src/charting/seqsee.rs
@@ -0,0 +1,234 @@
+use std::{collections::BTreeSet, fmt::Display, io};
+
+use serde_json::{Map, Value, json};
+
+use crate::{
+    charting::{Backend, Orientation},
+    coordinates::{Bidegree, BidegreeGenerator},
+};
+
+/// A [`Backend`] that emits [SeqSee](https://github.com/JoeyBF/SeqSee) JSON.
+///
+/// SeqSee is a generic visualization tool for spectral sequences. It consumes a JSON file
+/// conforming to its [schema] and produces a self-contained, interactive HTML chart. This backend
+/// targets that schema so that the charts produced elsewhere in this crate can be rendered by
+/// SeqSee.
+///
+/// The document is assembled in memory and written out when the backend is dropped, since the JSON
+/// object must group all nodes together and all edges together, whereas the [`Backend`] callbacks
+/// interleave them.
+///
+/// [schema]: https://raw.githubusercontent.com/JoeyBF/SeqSee/refs/heads/master/seqsee/input_schema.json
+pub struct SeqSeeBackend<T: io::Write> {
+    out: T,
+    max: Bidegree,
+    /// Map from node id to its SeqSee node object.
+    nodes: Map<String, Value>,
+    /// The list of SeqSee edge objects.
+    edges: Vec<Value>,
+    /// The set of style names referenced by edges. Each becomes an attribute alias in the header so
+    /// that the edges referencing it validate against the schema.
+    styles: BTreeSet<String>,
+}
+
+impl<T: io::Write> SeqSeeBackend<T> {
+    pub fn new(out: T) -> Self {
+        Self {
+            out,
+            max: Bidegree::zero(),
+            nodes: Map::new(),
+            edges: Vec::new(),
+            styles: BTreeSet::new(),
+        }
+    }
+}
+
+/// Whether a style name denotes a differential, i.e. it is `d` followed by a page number.
+///
+/// Differentials are given a distinct color to match the other backends in this crate.
+fn is_differential(style: &str) -> bool {
+    style
+        .strip_prefix('d')
+        .is_some_and(|rest| !rest.is_empty() && rest.bytes().all(|b| b.is_ascii_digit()))
+}
+
+impl<T: io::Write> Backend for SeqSeeBackend<T> {
+    type Error = io::Error;
+
+    const EXT: &'static str = "json";
+
+    fn header(&mut self, max: Bidegree) -> Result<(), Self::Error> {
+        self.max = max;
+        Ok(())
+    }
+
+    // SeqSee draws its own grid based on the chart dimensions in the header, so there is nothing to
+    // emit for the grid lines.
+    fn line(&mut self, _start: Bidegree, _end: Bidegree, _style: &str) -> Result<(), Self::Error> {
+        Ok(())
+    }
+
+    // SeqSee draws its own axis labels, so there is nothing to emit here.
+    fn text(
+        &mut self,
+        _b: Bidegree,
+        _content: impl Display,
+        _orientation: Orientation,
+    ) -> Result<(), Self::Error> {
+        Ok(())
+    }
+
+    fn node(&mut self, b: Bidegree, n: usize) -> Result<(), Self::Error> {
+        if n == 0 || b.x() > self.max.x() || b.y() > self.max.y() {
+            return Ok(());
+        }
+
+        for k in 0..n {
+            // The `{:#}` (alternate) form of the `Display` impl is `(x,y,idx)`. Reusing it here and
+            // in `structline` keeps node ids and edge endpoints in sync.
+            let id = format!("{:#}", BidegreeGenerator::new(b, k));
+            self.nodes.insert(
+                id,
+                json!({
+                    "x": b.x(),
+                    "y": b.y(),
+                    "position": k,
+                }),
+            );
+        }
+        Ok(())
+    }
+
+    fn structline(
+        &mut self,
+        source: BidegreeGenerator,
+        target: BidegreeGenerator,
+        style: Option<&str>,
+    ) -> Result<(), Self::Error> {
+        if source.x() > self.max.x()
+            || source.y() > self.max.y()
+            || target.x() > self.max.x()
+            || target.y() > self.max.y()
+        {
+            return Ok(());
+        }
+
+        let mut edge = Map::new();
+        edge.insert("source".to_string(), Value::String(format!("{source:#}")));
+        edge.insert("target".to_string(), Value::String(format!("{target:#}")));
+        if let Some(style) = style {
+            self.styles.insert(style.to_string());
+            edge.insert("attributes".to_string(), json!([style]));
+        }
+        self.edges.push(Value::Object(edge));
+        Ok(())
+    }
+}
+
+impl<T: io::Write> Drop for SeqSeeBackend<T> {
+    fn drop(&mut self) {
+        // Register every referenced style as an attribute alias so that the edges validate.
+        let mut attributes = Map::new();
+        for style in &self.styles {
+            let attr = if is_differential(style) {
+                json!([{ "color": "blue" }])
+            } else {
+                json!([])
+            };
+            attributes.insert(style.clone(), attr);
+        }
+
+        let document = json!({
+            "header": {
+                "chart": {
+                    "width": { "min": 0, "max": self.max.x() },
+                    "height": { "min": 0, "max": self.max.y() },
+                },
+                "aliases": {
+                    "attributes": attributes,
+                },
+            },
+            "nodes": std::mem::take(&mut self.nodes),
+            "edges": std::mem::take(&mut self.edges),
+        });
+
+        let _ = serde_json::to_writer_pretty(&mut self.out, &document);
+        let _ = writeln!(self.out);
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_seqsee_output() {
+        let mut buf: Vec<u8> = Vec::new();
+        {
+            let mut backend = SeqSeeBackend::new(&mut buf);
+            // `init` draws the grid and axis labels via `line`/`text`, which are no-ops here.
+            backend.init(Bidegree::x_y(2, 2)).unwrap();
+
+            backend.node(Bidegree::x_y(0, 0), 1).unwrap();
+            backend.node(Bidegree::x_y(0, 1), 1).unwrap();
+            backend.node(Bidegree::x_y(1, 1), 1).unwrap();
+
+            // A multiplication by `h0` (a filtration-one product).
+            backend
+                .structline(
+                    BidegreeGenerator::new(Bidegree::x_y(0, 0), 0),
+                    BidegreeGenerator::new(Bidegree::x_y(0, 1), 0),
+                    Some("h0"),
+                )
+                .unwrap();
+            // A `d2` differential.
+            backend
+                .structline(
+                    BidegreeGenerator::new(Bidegree::x_y(1, 1), 0),
+                    BidegreeGenerator::new(Bidegree::x_y(0, 1), 0),
+                    Some("d2"),
+                )
+                .unwrap();
+            // Out of bounds: dropped silently.
+            backend.node(Bidegree::x_y(5, 5), 1).unwrap();
+        }
+
+        // Compare parsed values rather than the raw string so the assertion does not depend on
+        // JSON object key ordering, which varies with whether serde_json's `preserve_order`
+        // feature is enabled by feature unification in the surrounding build.
+        let produced: Value = serde_json::from_slice(&buf).unwrap();
+        let expected = json!({
+            "header": {
+                "chart": {
+                    "width": { "min": 0, "max": 2 },
+                    "height": { "min": 0, "max": 2 },
+                },
+                "aliases": {
+                    "attributes": {
+                        "h0": [],
+                        "d2": [{ "color": "blue" }],
+                    },
+                },
+            },
+            "nodes": {
+                "(0,0,0)": { "x": 0, "y": 0, "position": 0 },
+                "(0,1,0)": { "x": 0, "y": 1, "position": 0 },
+                "(1,1,0)": { "x": 1, "y": 1, "position": 0 },
+            },
+            "edges": [
+                { "source": "(0,0,0)", "target": "(0,1,0)", "attributes": ["h0"] },
+                { "source": "(1,1,0)", "target": "(0,1,0)", "attributes": ["d2"] },
+            ],
+        });
+        assert_eq!(produced, expected);
+    }
+
+    #[test]
+    fn test_is_differential() {
+        assert!(is_differential("d2"));
+        assert!(is_differential("d17"));
+        assert!(!is_differential("d"));
+        assert!(!is_differential("h0"));
+        assert!(!is_differential("delta"));
+    }
+}
diff --git a/ext/examples/chart.rs b/ext/examples/chart.rs
index 5cb02c9258..7b55bffcb4 100644
--- a/ext/examples/chart.rs
+++ b/ext/examples/chart.rs
@@ -3,13 +3,20 @@ use ext::{
     chain_complex::{ChainComplex, FreeChainComplex},
     utils::query_module,
 };
-use sseq::charting::SvgBackend;
+use sseq::charting::{SeqSeeBackend, SvgBackend, TikzBackend};
 
 fn main() -> anyhow::Result<()> {
     ext::utils::init_logging()?;
 
     let resolution = query_module(None, false)?;
 
+    let format = query::with_default("Output format (svg/tikz/seqsee)", "svg", |x| match x {
+        "svg" | "tikz" | "seqsee" => Ok(x.to_string()),
+        _ => Err(format!(
+            "unknown format '{x}'; expected one of svg, tikz, seqsee"
+        )),
+    });
+
     let sseq = resolution.to_sseq();
     let products: Vec<_> = resolution
         .algebra()
@@ -18,12 +25,20 @@ fn main() -> anyhow::Result<()> {
         .map(|(name, op_deg, op_idx)| (name, resolution.filtration_one_products(op_deg, op_idx)))
         .collect();
 
-    sseq.write_to_graph(
-        SvgBackend::new(std::io::stdout()),
-        2,
-        false,
-        products.iter(),
-        |_| Ok(()),
-    )?;
+    let out = std::io::stdout();
+    match format.as_str() {
+        "svg" => {
+            sseq.write_to_graph(SvgBackend::new(out), 2, false, products.iter(), |_| Ok(()))?
+        }
+        "tikz" => {
+            sseq.write_to_graph(TikzBackend::new(out), 2, false, products.iter(), |_| Ok(()))?
+        }
+        "seqsee" => {
+            sseq.write_to_graph(SeqSeeBackend::new(out), 2, false, products.iter(), |_| {
+                Ok(())
+            })?
+        }
+        _ => unreachable!(),
+    }
     Ok(())
 }