diff --git a/Cargo.lock b/Cargo.lock
index e14e4e8..20a67e0 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2263,6 +2263,8 @@ name = "ely_browser_core"
 version = "0.1.0"
 dependencies = [
  "ely_domain",
+ "serde",
+ "serde_json",
  "thiserror 2.0.18",
  "url",
 ]
diff --git a/crates/ely_browser_core/Cargo.toml b/crates/ely_browser_core/Cargo.toml
index 07d8b25..8c1284f 100644
--- a/crates/ely_browser_core/Cargo.toml
+++ b/crates/ely_browser_core/Cargo.toml
@@ -7,6 +7,8 @@ rust-version.workspace = true
 
 [dependencies]
 ely_domain = { path = "../ely_domain" }
+serde.workspace = true
+serde_json.workspace = true
 thiserror.workspace = true
 url.workspace = true
 
diff --git a/crates/ely_browser_core/src/error.rs b/crates/ely_browser_core/src/error.rs
index 1c8eccf..4aeae0b 100644
--- a/crates/ely_browser_core/src/error.rs
+++ b/crates/ely_browser_core/src/error.rs
@@ -18,6 +18,9 @@ pub enum CoreError {
     #[error("space not found: {id}")]
     SpaceNotFound { id: SpaceId },
 
+    #[error("invalid .elyspace package: {reason}")]
+    InvalidSpacePackage { reason: String },
+
     #[error("trashed space not found: {id}")]
     TrashedSpaceNotFound { id: SpaceId },
 
diff --git a/crates/ely_browser_core/src/lib.rs b/crates/ely_browser_core/src/lib.rs
index 0c473cb..c44e407 100644
--- a/crates/ely_browser_core/src/lib.rs
+++ b/crates/ely_browser_core/src/lib.rs
@@ -4,6 +4,7 @@ mod state;
 
 pub use error::CoreError;
 pub use state::{
-    BrowserCore, BrowserSnapshot, InitialBrowserConfig, InstalledPlugin, PluginAuditAction,
-    PluginAuditEvent, SiteDataClearance, TrashedSpace,
+    BrowserCore, BrowserSnapshot, ELYSPACE_FILE_EXTENSION, ELYSPACE_SCHEMA_VERSION,
+    ElySpacePackage, InitialBrowserConfig, InstalledPlugin, PluginAuditAction, PluginAuditEvent,
+    SiteDataClearance, SpaceImportProfileMapping, TrashedSpace,
 };
diff --git a/crates/ely_browser_core/src/state.rs b/crates/ely_browser_core/src/state.rs
index fb101f2..d0a074e 100644
--- a/crates/ely_browser_core/src/state.rs
+++ b/crates/ely_browser_core/src/state.rs
@@ -21,6 +21,7 @@ mod profiles;
 mod reading_list;
 mod site_data;
 mod site_permissions;
+mod space_exports;
 mod spaces;
 mod splits;
 mod sync;
@@ -33,6 +34,9 @@ mod tabs;
 
 pub use plugins::{InstalledPlugin, PluginAuditAction, PluginAuditEvent};
 pub use site_data::SiteDataClearance;
+pub use space_exports::{
+    ELYSPACE_FILE_EXTENSION, ELYSPACE_SCHEMA_VERSION, ElySpacePackage, SpaceImportProfileMapping,
+};
 pub use spaces::TrashedSpace;
 
 #[derive(Clone, Debug)]
diff --git a/crates/ely_browser_core/src/state/space_exports.rs b/crates/ely_browser_core/src/state/space_exports.rs
new file mode 100644
index 0000000..2e2257a
--- /dev/null
+++ b/crates/ely_browser_core/src/state/space_exports.rs
@@ -0,0 +1,295 @@
+use ely_domain::{
+    ArchivePolicy, BrowserTab, ProfileId, ProfileKind, Space, SpaceId, TabId, UrlText,
+};
+use serde::{Deserialize, Serialize};
+
+use super::BrowserCore;
+use crate::CoreError;
+
+pub const ELYSPACE_SCHEMA_VERSION: u16 = 1;
+pub const ELYSPACE_FILE_EXTENSION: &str = "elyspace";
+
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum SpaceImportProfileMapping {
+    PreserveExisting,
+    UseActiveProfile,
+}
+
+#[derive(Clone, Debug, Deserialize, Eq, PartialEq, Serialize)]
+#[serde(deny_unknown_fields)]
+pub struct ElySpacePackage {
+    version: u16,
+    space: ElySpaceRecord,
+    tabs: Vec<ElySpaceTabRecord>,
+}
+
+impl ElySpacePackage {
+    #[must_use]
+    pub fn version(&self) -> u16 {
+        self.version
+    }
+
+    #[must_use]
+    pub fn space_name(&self) -> &str {
+        &self.space.name
+    }
+
+    #[must_use]
+    pub fn tab_count(&self) -> usize {
+        self.tabs.len()
+    }
+}
+
+#[derive(Clone, Debug, Deserialize, Eq, PartialEq, Serialize)]
+#[serde(deny_unknown_fields)]
+struct ElySpaceRecord {
+    name: String,
+    icon: String,
+    accent_hex: u32,
+    default_profile_id: String,
+    archive_policy: ElySpaceArchivePolicy,
+    sidebar_width_px: u16,
+}
+
+#[derive(Clone, Debug, Deserialize, Eq, PartialEq, Serialize)]
+#[serde(deny_unknown_fields)]
+struct ElySpaceTabRecord {
+    title: String,
+    url: String,
+    profile_id: String,
+    favicon_key: Option<String>,
+    pinned: bool,
+    favorite: bool,
+    sort_key: u64,
+    sync_enabled: bool,
+}
+
+#[derive(Clone, Debug, Deserialize, Eq, PartialEq, Serialize)]
+#[serde(tag = "kind", rename_all = "snake_case")]
+enum ElySpaceArchivePolicy {
+    Manual,
+    IdleDays { days: u16 },
+}
+
+impl BrowserCore {
+    pub fn export_space_package_json(&self, space_id: &SpaceId) -> Result<String, CoreError> {
+        serde_json::to_string_pretty(&self.export_space_package(space_id)?)
+            .map_err(invalid_space_package)
+    }
+
+    pub fn export_space_package(&self, space_id: &SpaceId) -> Result<ElySpacePackage, CoreError> {
+        let space = self
+            .spaces
+            .iter()
+            .find(|space| space.id() == space_id)
+            .ok_or_else(|| CoreError::SpaceNotFound { id: space_id.clone() })?;
+        let tabs = self
+            .tabs
+            .iter()
+            .filter(|tab| tab.space_id() == space_id)
+            .map(ElySpaceTabRecord::from_tab)
+            .collect();
+
+        Ok(ElySpacePackage {
+            version: ELYSPACE_SCHEMA_VERSION,
+            space: ElySpaceRecord::from_space(space),
+            tabs,
+        })
+    }
+
+    pub fn import_space_package_json(
+        &mut self,
+        package_json: &str,
+        profile_mapping: SpaceImportProfileMapping,
+    ) -> Result<SpaceId, CoreError> {
+        let package = serde_json::from_str(package_json).map_err(invalid_space_package)?;
+        self.import_space_package(package, profile_mapping)
+    }
+
+    pub fn import_space_package(
+        &mut self,
+        package: ElySpacePackage,
+        profile_mapping: SpaceImportProfileMapping,
+    ) -> Result<SpaceId, CoreError> {
+        validate_package_version(package.version)?;
+        self.validate_imported_favorites(&package)?;
+        let default_profile_id = self.imported_default_profile_id(&package, profile_mapping)?;
+        let sort_key = self.next_space_sort_key();
+        let mut space = Space::new(
+            package.space.name.clone(),
+            package.space.icon.clone(),
+            package.space.accent_hex,
+            default_profile_id.clone(),
+            sort_key,
+        );
+        space.set_archive_policy(package.space.archive_policy.clone().into());
+        space.set_sidebar_width_px(package.space.sidebar_width_px);
+
+        let space_id = space.id().clone();
+        let tabs = self.imported_tabs(&space_id, &default_profile_id, &package, profile_mapping)?;
+        let active_tab_id = tabs[0].id().clone();
+
+        self.spaces.push(space);
+        self.tabs.extend(tabs);
+        self.active_tabs_by_space.insert(space_id.clone(), active_tab_id.clone());
+        self.select_tab(&active_tab_id)?;
+        Ok(space_id)
+    }
+
+    fn imported_default_profile_id(
+        &self,
+        package: &ElySpacePackage,
+        profile_mapping: SpaceImportProfileMapping,
+    ) -> Result<ProfileId, CoreError> {
+        match profile_mapping {
+            SpaceImportProfileMapping::PreserveExisting => {
+                let profile_id = ProfileId::parse(&package.space.default_profile_id)?;
+                self.standard_profile_id(&profile_id)?;
+                Ok(profile_id)
+            }
+            SpaceImportProfileMapping::UseActiveProfile => self.stable_active_profile_id(),
+        }
+    }
+
+    fn validate_imported_favorites(&self, package: &ElySpacePackage) -> Result<(), CoreError> {
+        let imported_favorites = package.tabs.iter().filter(|tab| tab.favorite).count();
+        let favorite_limit = self.favorite_limit.value();
+        if self.favorites().len() + imported_favorites > favorite_limit {
+            return Err(CoreError::FavoriteLimitReached { limit: favorite_limit });
+        }
+        Ok(())
+    }
+
+    fn imported_tabs(
+        &self,
+        space_id: &SpaceId,
+        default_profile_id: &ProfileId,
+        package: &ElySpacePackage,
+        profile_mapping: SpaceImportProfileMapping,
+    ) -> Result<Vec<BrowserTab>, CoreError> {
+        let mut tabs = package
+            .tabs
+            .iter()
+            .map(|tab| self.imported_tab(space_id, default_profile_id, tab, profile_mapping))
+            .collect::<Result<Vec<_>, _>>()?;
+
+        if tabs.is_empty() {
+            tabs.push(self.build_tab_for(
+                space_id.clone(),
+                default_profile_id.clone(),
+                self.new_tab_url()?,
+            ));
+        }
+        Ok(tabs)
+    }
+
+    fn imported_tab(
+        &self,
+        space_id: &SpaceId,
+        default_profile_id: &ProfileId,
+        record: &ElySpaceTabRecord,
+        profile_mapping: SpaceImportProfileMapping,
+    ) -> Result<BrowserTab, CoreError> {
+        let profile_id = match profile_mapping {
+            SpaceImportProfileMapping::PreserveExisting => {
+                let profile_id = ProfileId::parse(&record.profile_id)?;
+                self.standard_profile_id(&profile_id)?;
+                profile_id
+            }
+            SpaceImportProfileMapping::UseActiveProfile => default_profile_id.clone(),
+        };
+        let mut tab = BrowserTab::new(
+            TabId::new(),
+            space_id.clone(),
+            profile_id,
+            record.title.clone(),
+            UrlText::parse(&record.url)?,
+        )
+        .with_sort_key(record.sort_key);
+        tab.set_pinned(record.pinned);
+        tab.set_favorite(record.favorite);
+        tab.set_sync_enabled(record.sync_enabled);
+        if let Some(favicon_key) = &record.favicon_key {
+            tab.set_favicon_key(favicon_key.clone())?;
+        }
+        Ok(tab)
+    }
+
+    fn standard_profile_id(&self, profile_id: &ProfileId) -> Result<(), CoreError> {
+        let profile = self
+            .profiles
+            .iter()
+            .find(|profile| profile.id() == profile_id)
+            .ok_or_else(|| CoreError::ProfileNotFound { id: profile_id.clone() })?;
+        if profile.kind() == &ProfileKind::Private {
+            return Err(CoreError::PrivateProfileDefaultLocked { id: profile_id.clone() });
+        }
+        Ok(())
+    }
+
+    fn stable_active_profile_id(&self) -> Result<ProfileId, CoreError> {
+        if self.active_profile()?.kind() == &ProfileKind::Private {
+            Ok(self.active_space()?.default_profile_id().clone())
+        } else {
+            Ok(self.active_profile_id.clone())
+        }
+    }
+}
+
+impl ElySpaceRecord {
+    fn from_space(space: &Space) -> Self {
+        Self {
+            name: space.name().to_string(),
+            icon: space.icon().to_string(),
+            accent_hex: space.accent_hex(),
+            default_profile_id: space.default_profile_id().as_str().to_string(),
+            archive_policy: ElySpaceArchivePolicy::from(space.archive_policy()),
+            sidebar_width_px: space.sidebar_width_px(),
+        }
+    }
+}
+
+impl ElySpaceTabRecord {
+    fn from_tab(tab: &BrowserTab) -> Self {
+        Self {
+            title: tab.title().to_string(),
+            url: tab.url().as_str().to_string(),
+            profile_id: tab.profile_id().as_str().to_string(),
+            favicon_key: tab.favicon_key().map(str::to_string),
+            pinned: tab.flags().pinned,
+            favorite: tab.flags().favorite,
+            sort_key: tab.sort_key(),
+            sync_enabled: tab.sync_enabled(),
+        }
+    }
+}
+
+impl From<&ArchivePolicy> for ElySpaceArchivePolicy {
+    fn from(policy: &ArchivePolicy) -> Self {
+        match policy {
+            ArchivePolicy::Manual => Self::Manual,
+            ArchivePolicy::IdleDays(days) => Self::IdleDays { days: *days },
+        }
+    }
+}
+
+impl From<ElySpaceArchivePolicy> for ArchivePolicy {
+    fn from(policy: ElySpaceArchivePolicy) -> Self {
+        match policy {
+            ElySpaceArchivePolicy::Manual => Self::Manual,
+            ElySpaceArchivePolicy::IdleDays { days } => Self::IdleDays(days),
+        }
+    }
+}
+
+fn validate_package_version(version: u16) -> Result<(), CoreError> {
+    if version == ELYSPACE_SCHEMA_VERSION {
+        Ok(())
+    } else {
+        Err(CoreError::InvalidSpacePackage { reason: format!("unsupported version {version}") })
+    }
+}
+
+fn invalid_space_package(error: serde_json::Error) -> CoreError {
+    CoreError::InvalidSpacePackage { reason: error.to_string() }
+}
diff --git a/crates/ely_browser_core/tests/space_exports.rs b/crates/ely_browser_core/tests/space_exports.rs
new file mode 100644
index 0000000..12ce2f6
--- /dev/null
+++ b/crates/ely_browser_core/tests/space_exports.rs
@@ -0,0 +1,135 @@
+use std::error::Error;
+
+use ely_browser_core::{
+    BrowserCore, CoreError, ELYSPACE_FILE_EXTENSION, ELYSPACE_SCHEMA_VERSION, InitialBrowserConfig,
+    SpaceImportProfileMapping,
+};
+use ely_domain::{ArchivePolicy, ProfileKind, UrlText};
+use serde_json::Value;
+
+#[test]
+fn exports_space_package_json_with_settings_and_tabs() -> Result<(), Box<dyn Error>> {
+    let mut core = BrowserCore::new(InitialBrowserConfig::ely_defaults()?)?;
+    let space_id = core.snapshot()?.active_space_id;
+    let active_tab_id = core.snapshot()?.active_tab_id;
+
+    core.set_space_archive_policy(&space_id, ArchivePolicy::IdleDays(14))?;
+    core.set_space_sidebar_width(&space_id, 320)?;
+    core.set_tab_favicon_key(&active_tab_id, "favicons/work.ico")?;
+    core.toggle_active_tab_pinned()?;
+    core.toggle_active_tab_favorite()?;
+    core.open_tab(UrlText::parse("https://servo.org/")?);
+
+    let package = core.export_space_package(&space_id)?;
+    let package_json = core.export_space_package_json(&space_id)?;
+    let value: Value = serde_json::from_str(&package_json)?;
+
+    assert_eq!(ELYSPACE_FILE_EXTENSION, "elyspace");
+    assert_eq!(package.version(), ELYSPACE_SCHEMA_VERSION);
+    assert_eq!(package.space_name(), "Work");
+    assert_eq!(package.tab_count(), 2);
+    assert_eq!(json_u64(&value, "version")?, 1);
+    assert_eq!(json_str(json_object(&value, "space")?, "name")?, "Work");
+    assert_eq!(json_object_u64(json_object(&value, "space")?, "sidebar_width_px")?, 320);
+    assert_eq!(json_array(&value, "tabs")?.len(), 2);
+    Ok(())
+}
+
+#[test]
+fn imports_space_package_with_active_profile_mapping() -> Result<(), Box<dyn Error>> {
+    let mut source = BrowserCore::new(InitialBrowserConfig::ely_defaults()?)?;
+    let source_space_id = source.snapshot()?.active_space_id;
+    source.set_space_archive_policy(&source_space_id, ArchivePolicy::IdleDays(7))?;
+    source.set_space_sidebar_width(&source_space_id, 360)?;
+    source.open_tab(UrlText::parse("https://example.com")?);
+    let package_json = source.export_space_package_json(&source_space_id)?;
+
+    let mut target = BrowserCore::new(InitialBrowserConfig::ely_defaults()?)?;
+    let target_profile_id = target.snapshot()?.active_profile_id;
+    let imported_space_id = target
+        .import_space_package_json(&package_json, SpaceImportProfileMapping::UseActiveProfile)?;
+    let snapshot = target.snapshot()?;
+    let Some(imported_space) =
+        snapshot.spaces.iter().find(|space| space.id() == &imported_space_id)
+    else {
+        return Err("missing imported space".into());
+    };
+
+    assert_eq!(imported_space.name(), "Work");
+    assert_eq!(imported_space.archive_policy(), &ArchivePolicy::IdleDays(7));
+    assert_eq!(imported_space.sidebar_width_px(), 360);
+    assert_eq!(imported_space.default_profile_id(), &target_profile_id);
+    assert!(snapshot.tabs.iter().all(|tab| tab.profile_id() == &target_profile_id));
+    assert!(snapshot.tabs.iter().any(|tab| tab.url().as_str() == "https://example.com"));
+    Ok(())
+}
+
+#[test]
+fn imports_space_package_with_existing_profile_mapping() -> Result<(), Box<dyn Error>> {
+    let mut core = BrowserCore::new(InitialBrowserConfig::ely_defaults()?)?;
+    let research_profile_id = core.create_profile("Research", 0x9fc9a2, ProfileKind::Standard)?;
+    let research_space_id = core.create_space("Research", "R", 0x9fc9a2)?;
+    core.open_tab(UrlText::parse("https://servo.org/")?);
+    let package_json = core.export_space_package_json(&research_space_id)?;
+
+    let imported_space_id =
+        core.import_space_package_json(&package_json, SpaceImportProfileMapping::PreserveExisting)?;
+    let snapshot = core.snapshot()?;
+    let Some(imported_space) =
+        snapshot.spaces.iter().find(|space| space.id() == &imported_space_id)
+    else {
+        return Err("missing imported space".into());
+    };
+
+    assert_eq!(imported_space.default_profile_id(), &research_profile_id);
+    assert!(snapshot.tabs.iter().all(|tab| tab.profile_id() == &research_profile_id));
+    Ok(())
+}
+
+#[test]
+fn importing_space_package_rejects_missing_preserved_profile() -> Result<(), Box<dyn Error>> {
+    let source = BrowserCore::new(InitialBrowserConfig::ely_defaults()?)?;
+    let source_profile_id = source.snapshot()?.active_profile_id;
+    let source_space_id = source.snapshot()?.active_space_id;
+    let package_json = source.export_space_package_json(&source_space_id)?;
+
+    let mut target = BrowserCore::new(InitialBrowserConfig::ely_defaults()?)?;
+    let error = match target
+        .import_space_package_json(&package_json, SpaceImportProfileMapping::PreserveExisting)
+    {
+        Err(error) => error,
+        Ok(_) => return Err("import should reject missing preserved profile".into()),
+    };
+
+    assert_eq!(error, CoreError::ProfileNotFound { id: source_profile_id });
+    Ok(())
+}
+
+fn json_object<'a>(
+    value: &'a Value,
+    key: &str,
+) -> Result<&'a serde_json::Map<String, Value>, Box<dyn Error>> {
+    value.get(key).and_then(Value::as_object).ok_or_else(|| format!("missing object {key}").into())
+}
+
+fn json_array<'a>(value: &'a Value, key: &str) -> Result<&'a Vec<Value>, Box<dyn Error>> {
+    value.get(key).and_then(Value::as_array).ok_or_else(|| format!("missing array {key}").into())
+}
+
+fn json_str<'a>(
+    value: &'a serde_json::Map<String, Value>,
+    key: &str,
+) -> Result<&'a str, Box<dyn Error>> {
+    value.get(key).and_then(Value::as_str).ok_or_else(|| format!("missing string {key}").into())
+}
+
+fn json_object_u64(
+    value: &serde_json::Map<String, Value>,
+    key: &str,
+) -> Result<u64, Box<dyn Error>> {
+    value.get(key).and_then(Value::as_u64).ok_or_else(|| format!("missing number {key}").into())
+}
+
+fn json_u64(value: &Value, key: &str) -> Result<u64, Box<dyn Error>> {
+    value.get(key).and_then(Value::as_u64).ok_or_else(|| format!("missing number {key}").into())
+}