diff --git a/rslib/Cargo.toml b/rslib/Cargo.toml
index 94707c0d3..0bb56f85e 100644
--- a/rslib/Cargo.toml
+++ b/rslib/Cargo.toml
@@ -23,7 +23,7 @@ unicode-normalization = "0.1.12"
 tempfile = "3.1.0"
 serde = "1.0.104"
 serde_json = "1.0.45"
-tokio = "0.2.11"
+tokio = { version = "0.2.11", features = ["fs"] }
 serde_derive = "1.0.104"
 zip = "0.5.4"
 serde_tuple = "0.4.0"
@@ -47,6 +47,8 @@ rand = "0.7.3"
 num-integer = "0.1.42"
 itertools = "0.9.0"
 flate2 = "1.0.14"
+pin-project = "0.4.17"
+async-compression = { version = "0.3.4", features = ["stream", "gzip"] }
 
 [target.'cfg(target_vendor="apple")'.dependencies.rusqlite]
 version = "0.23.1"
@@ -57,12 +59,15 @@ version = "0.23.1"
 features = ["trace", "functions", "collation", "bundled"]
 
 [target.'cfg(linux)'.dependencies]
-reqwest = { version = "0.10.1", features = ["json", "socks", "native-tls-vendored"] }
+reqwest = { version = "0.10.1", features = ["json", "socks", "stream", "native-tls-vendored"] }
 
 [target.'cfg(not(linux))'.dependencies]
-reqwest = { version = "0.10.1", features = ["json", "socks"] }
+reqwest = { version = "0.10.1", features = ["json", "socks", "stream" ] }
 
 [build-dependencies]
 prost-build = "0.6.1"
 fluent-syntax = "0.9.2"
 
+[dev-dependencies]
+env_logger = "0.7.1"
+
diff --git a/rslib/src/sync/http_client.rs b/rslib/src/sync/http_client.rs
index 6071eb7fb..1e855db8f 100644
--- a/rslib/src/sync/http_client.rs
+++ b/rslib/src/sync/http_client.rs
@@ -2,13 +2,16 @@
 // License: GNU AGPL, version 3 or later; http://www.gnu.org/licenses/agpl.html
 
 use super::*;
+use bytes::Bytes;
+use futures::Stream;
+use reqwest::Body;
 
 static SYNC_VERSION: u8 = 10;
-pub struct HTTPSyncClient<'a> {
+pub struct HTTPSyncClient {
     hkey: Option<String>,
     skey: String,
     client: Client,
-    endpoint: &'a str,
+    endpoint: String,
 }
 
 #[derive(Serialize)]
@@ -68,14 +71,15 @@ struct SanityCheckIn {
 #[derive(Serialize)]
 struct Empty {}
 
-impl HTTPSyncClient<'_> {
-    pub fn new<'a>(endpoint: &'a str) -> HTTPSyncClient<'a> {
+impl HTTPSyncClient {
+    pub fn new<'a>(endpoint_suffix: &str) -> HTTPSyncClient {
         let client = Client::builder()
             .connect_timeout(Duration::from_secs(30))
             .timeout(Duration::from_secs(60))
             .build()
             .unwrap();
         let skey = guid();
+        let endpoint = endpoint(&endpoint_suffix);
         HTTPSyncClient {
             hkey: None,
             skey,
@@ -84,7 +88,7 @@ impl HTTPSyncClient<'_> {
         }
     }
 
-    async fn json_request<T>(&self, method: &str, json: &T) -> Result<Response>
+    async fn json_request<T>(&self, method: &str, json: &T, timeout_long: bool) -> Result<Response>
     where
         T: serde::Serialize,
     {
@@ -94,7 +98,7 @@ impl HTTPSyncClient<'_> {
         gz.write_all(&req_json)?;
         let part = multipart::Part::bytes(gz.finish()?);
 
-        self.request(method, part).await
+        self.request(method, part, timeout_long).await
     }
 
     async fn json_request_deserialized<T, T2>(&self, method: &str, json: &T) -> Result<T2>
@@ -102,14 +106,19 @@ impl HTTPSyncClient<'_> {
         T: Serialize,
         T2: DeserializeOwned,
     {
-        self.json_request(method, json)
+        self.json_request(method, json, false)
             .await?
             .json()
             .await
             .map_err(Into::into)
     }
 
-    async fn request(&self, method: &str, data_part: multipart::Part) -> Result<Response> {
+    async fn request(
+        &self,
+        method: &str,
+        data_part: multipart::Part,
+        timeout_long: bool,
+    ) -> Result<Response> {
         let data_part = data_part.file_name("data");
 
         let mut form = multipart::Form::new()
@@ -120,12 +129,16 @@ impl HTTPSyncClient<'_> {
         }
 
         let url = format!("{}{}", self.endpoint, method);
-        let req = self.client.post(&url).multipart(form);
+        let mut req = self.client.post(&url).multipart(form);
+
+        if timeout_long {
+            req = req.timeout(Duration::from_secs(60 * 60));
+        }
 
         req.send().await?.error_for_status().map_err(Into::into)
     }
 
-    async fn login(&mut self, username: &str, password: &str) -> Result<()> {
+    pub(crate) async fn login(&mut self, username: &str, password: &str) -> Result<()> {
         let resp: HostKeyOut = self
             .json_request_deserialized("hostKey", &HostKeyIn { username, password })
             .await?;
@@ -138,7 +151,7 @@ impl HTTPSyncClient<'_> {
         self.hkey.as_ref().unwrap()
     }
 
-    async fn meta(&mut self) -> Result<ServerMeta> {
+    pub(crate) async fn meta(&self) -> Result<ServerMeta> {
         let meta_in = MetaIn {
             sync_version: SYNC_VERSION,
             client_version: sync_client_version(),
@@ -146,49 +159,168 @@ impl HTTPSyncClient<'_> {
         self.json_request_deserialized("meta", &meta_in).await
     }
 
-    async fn start(&mut self, input: &StartIn) -> Result<Graves> {
-        self.json_request_deserialized("start", input).await
+    pub(crate) async fn start(
+        &self,
+        minimum_usn: Usn,
+        minutes_west: i32,
+        client_is_newer: bool,
+    ) -> Result<Graves> {
+        let input = StartIn {
+            minimum_usn,
+            minutes_west,
+            client_is_newer,
+            client_graves: None,
+        };
+        self.json_request_deserialized("start", &input).await
     }
 
-    async fn apply_graves(&mut self, chunk: Graves) -> Result<()> {
+    pub(crate) async fn apply_graves(&self, chunk: Graves) -> Result<()> {
         let input = ApplyGravesIn { chunk };
-        let resp = self.json_request("applyGraves", &input).await?;
+        let resp = self.json_request("applyGraves", &input, false).await?;
         resp.error_for_status()?;
         Ok(())
     }
 
-    async fn apply_changes(&mut self, changes: Changes) -> Result<Changes> {
+    pub(crate) async fn apply_changes(&self, changes: Changes) -> Result<Changes> {
         let input = ApplyChangesIn { changes };
         self.json_request_deserialized("applyChanges", &input).await
     }
 
-    async fn chunk(&mut self) -> Result<Chunk> {
+    pub(crate) async fn chunk(&self) -> Result<Chunk> {
         self.json_request_deserialized("chunk", &Empty {}).await
     }
 
-    async fn apply_chunk(&mut self, chunk: Chunk) -> Result<()> {
+    pub(crate) async fn apply_chunk(&self, chunk: Chunk) -> Result<()> {
         let input = ApplyChunkIn { chunk };
-        let resp = self.json_request("applyChunk", &input).await?;
+        let resp = self.json_request("applyChunk", &input, false).await?;
         resp.error_for_status()?;
         Ok(())
     }
 
-    async fn sanity_check(&mut self, client: SanityCheckCounts) -> Result<SanityCheckOut> {
+    pub(crate) async fn sanity_check(&self, client: SanityCheckCounts) -> Result<SanityCheckOut> {
         let input = SanityCheckIn { client };
         self.json_request_deserialized("sanityCheck2", &input).await
     }
 
-    async fn finish(&mut self) -> Result<()> {
-        let resp = self.json_request("finish", &Empty {}).await?;
+    pub(crate) async fn finish(&self) -> Result<()> {
+        let resp = self.json_request("finish", &Empty {}, false).await?;
         resp.error_for_status()?;
         Ok(())
     }
 
-    async fn abort(&mut self) -> Result<()> {
-        let resp = self.json_request("abort", &Empty {}).await?;
+    pub(crate) async fn abort(&self) -> Result<()> {
+        let resp = self.json_request("abort", &Empty {}, false).await?;
         resp.error_for_status()?;
         Ok(())
     }
+
+    async fn download_inner(
+        &self,
+    ) -> Result<(
+        usize,
+        impl Stream<Item = std::result::Result<Bytes, reqwest::Error>>,
+    )> {
+        let resp: reqwest::Response = self.json_request("download", &Empty {}, true).await?;
+        let len = resp.content_length().unwrap_or_default();
+        Ok((len as usize, resp.bytes_stream()))
+    }
+
+    /// Download collection into a temporary file, returning it.
+    /// Caller should persist the file in the correct path after checking it.
+    pub(crate) async fn download<P>(&self, folder: &Path, progress_fn: P) -> Result<NamedTempFile>
+    where
+        P: Fn(&FullSyncProgress),
+    {
+        let mut temp_file = NamedTempFile::new_in(folder)?;
+        let (size, mut stream) = self.download_inner().await?;
+        let mut progress = FullSyncProgress {
+            transferred_bytes: 0,
+            total_bytes: size,
+        };
+        while let Some(chunk) = stream.next().await {
+            let chunk = chunk?;
+            temp_file.write_all(&chunk)?;
+            progress.transferred_bytes += chunk.len();
+            progress_fn(&progress);
+        }
+
+        Ok(temp_file)
+    }
+
+    async fn upload_inner(&self, body: Body) -> Result<()> {
+        let data_part = multipart::Part::stream(body);
+        let resp = self.request("upload", data_part, true).await?;
+        resp.error_for_status()?;
+        Ok(())
+    }
+
+    pub(crate) async fn upload<P>(&mut self, col_path: &Path, progress_fn: P) -> Result<()>
+    where
+        P: Fn(&FullSyncProgress) + Send + Sync + 'static,
+    {
+        let file = tokio::fs::File::open(col_path).await?;
+        let total_bytes = file.metadata().await?.len() as usize;
+        let wrap1 = ProgressWrapper {
+            reader: file,
+            progress_fn,
+            progress: FullSyncProgress {
+                transferred_bytes: 0,
+                total_bytes,
+            },
+        };
+        let wrap2 = async_compression::stream::GzipEncoder::new(wrap1);
+        let body = Body::wrap_stream(wrap2);
+        self.upload_inner(body).await?;
+
+        Ok(())
+    }
+}
+
+use futures::{
+    ready,
+    task::{Context, Poll},
+};
+use pin_project::pin_project;
+use std::pin::Pin;
+use tokio::io::AsyncRead;
+
+#[pin_project]
+struct ProgressWrapper<S, P> {
+    #[pin]
+    reader: S,
+    progress_fn: P,
+    progress: FullSyncProgress,
+}
+
+impl<S, P> Stream for ProgressWrapper<S, P>
+where
+    S: AsyncRead,
+    P: Fn(&FullSyncProgress),
+{
+    type Item = std::result::Result<Bytes, std::io::Error>;
+
+    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        let mut buf = vec![0; 16 * 1024];
+        let this = self.project();
+        match ready!(this.reader.poll_read(cx, &mut buf)) {
+            Ok(0) => Poll::Ready(None),
+            Ok(size) => {
+                buf.resize(size, 0);
+                this.progress.transferred_bytes += size;
+                (this.progress_fn)(&this.progress);
+                Poll::Ready(Some(Ok(Bytes::from(buf))))
+            }
+            Err(e) => Poll::Ready(Some(Err(e))),
+        }
+    }
+}
+
+fn endpoint(suffix: &str) -> String {
+    if let Ok(endpoint) = std::env::var("SYNC_ENDPOINT") {
+        endpoint
+    } else {
+        format!("https://sync{}.ankiweb.net/sync/", suffix)
+    }
 }
 
 #[cfg(test)]
@@ -197,10 +329,8 @@ mod test {
     use crate::err::SyncErrorKind;
     use tokio::runtime::Runtime;
 
-    static ENDPOINT: &'static str = "https://sync.ankiweb.net/sync/";
-
     async fn http_client_inner(username: String, password: String) -> Result<()> {
-        let mut syncer = HTTPSyncClient::new(ENDPOINT);
+        let mut syncer = HTTPSyncClient::new("");
 
         assert!(matches!(
             syncer.login("nosuchuser", "nosuchpass").await,
@@ -223,20 +353,13 @@ mod test {
             })
         ));
 
-        let input = StartIn {
-            minimum_usn: Usn(0),
-            minutes_west: 0,
-            client_is_newer: true,
-            client_graves: None,
-        };
-
-        let _graves = syncer.start(&input).await?;
+        let _graves = syncer.start(Usn(1), 0, true).await?;
 
         // aborting should now work
         syncer.abort().await?;
 
         // start again, and continue
-        let _graves = syncer.start(&input).await?;
+        let _graves = syncer.start(Usn(0), 0, true).await?;
 
         syncer.apply_graves(Graves::default()).await?;
 
@@ -268,6 +391,21 @@ mod test {
 
         syncer.finish().await?;
 
+        use tempfile::tempdir;
+
+        let dir = tempdir()?;
+        let out_path = syncer
+            .download(&dir.path(), |progress| {
+                println!("progress: {:?}", progress);
+            })
+            .await?;
+
+        syncer
+            .upload(&out_path.path(), |progress| {
+                println!("progress {:?}", progress);
+            })
+            .await?;
+
         Ok(())
     }
 
@@ -280,6 +418,7 @@ mod test {
             }
         };
         let pass = std::env::var("TEST_SYNC_PASS").unwrap();
+        env_logger::init();
 
         let mut rt = Runtime::new().unwrap();
         rt.block_on(http_client_inner(user, pass))
diff --git a/rslib/src/sync/mod.rs b/rslib/src/sync/mod.rs
index 907031e5f..bc843ff3a 100644
--- a/rslib/src/sync/mod.rs
+++ b/rslib/src/sync/mod.rs
@@ -14,18 +14,20 @@ use crate::{
 };
 use flate2::write::GzEncoder;
 use flate2::Compression;
+use futures::StreamExt;
 use reqwest::{multipart, Client, Response};
 use serde::{de::DeserializeOwned, Deserialize, Serialize};
 use serde_json::Value;
 use serde_tuple::Serialize_tuple;
 use std::io::prelude::*;
-use std::{collections::HashMap, time::Duration};
+use std::{collections::HashMap, path::Path, time::Duration};
+use tempfile::NamedTempFile;
 
 #[derive(Default, Debug)]
 pub struct SyncProgress {}
 
 #[derive(Serialize, Deserialize, Debug)]
-struct ServerMeta {
+pub struct ServerMeta {
     #[serde(rename = "mod")]
     modified: TimestampMillis,
     #[serde(rename = "scm")]
@@ -42,20 +44,20 @@ struct ServerMeta {
 }
 
 #[derive(Serialize, Deserialize, Debug, Default)]
-struct Graves {
+pub struct Graves {
     cards: Vec<CardID>,
     decks: Vec<DeckID>,
     notes: Vec<NoteID>,
 }
 
 #[derive(Serialize_tuple, Deserialize, Debug, Default)]
-struct DecksAndConfig {
+pub struct DecksAndConfig {
     decks: Vec<DeckSchema11>,
     config: Vec<DeckConfSchema11>,
 }
 
 #[derive(Serialize, Deserialize, Debug, Default)]
-struct Changes {
+pub struct Changes {
     #[serde(rename = "models")]
     notetypes: Vec<NoteTypeSchema11>,
     #[serde(rename = "decks")]
@@ -70,18 +72,18 @@ struct Changes {
 }
 
 #[derive(Serialize, Deserialize, Debug, Default)]
-struct Chunk {
+pub struct Chunk {
     done: bool,
-    #[serde(skip_serializing_if = "Vec::is_empty")]
+    #[serde(skip_serializing_if = "Vec::is_empty", default)]
     revlog: Vec<ReviewLogEntry>,
-    #[serde(skip_serializing_if = "Vec::is_empty")]
+    #[serde(skip_serializing_if = "Vec::is_empty", default)]
     cards: Vec<CardEntry>,
-    #[serde(skip_serializing_if = "Vec::is_empty")]
+    #[serde(skip_serializing_if = "Vec::is_empty", default)]
     notes: Vec<NoteEntry>,
 }
 
 #[derive(Serialize_tuple, Deserialize, Debug)]
-struct ReviewLogEntry {
+pub struct ReviewLogEntry {
     id: TimestampMillis,
     cid: CardID,
     usn: Usn,
@@ -97,7 +99,7 @@ struct ReviewLogEntry {
 }
 
 #[derive(Serialize_tuple, Deserialize, Debug)]
-struct NoteEntry {
+pub struct NoteEntry {
     id: NoteID,
     guid: String,
     #[serde(rename = "mid")]
@@ -114,7 +116,7 @@ struct NoteEntry {
 }
 
 #[derive(Serialize_tuple, Deserialize, Debug)]
-struct CardEntry {
+pub struct CardEntry {
     id: CardID,
     nid: NoteID,
     did: DeckID,
@@ -136,7 +138,7 @@ struct CardEntry {
 }
 
 #[derive(Serialize, Deserialize, Debug)]
-struct SanityCheckOut {
+pub struct SanityCheckOut {
     status: SanityCheckStatus,
     #[serde(rename = "c")]
     client: Option<SanityCheckCounts>,
@@ -152,7 +154,7 @@ enum SanityCheckStatus {
 }
 
 #[derive(Serialize_tuple, Deserialize, Debug)]
-struct SanityCheckCounts {
+pub struct SanityCheckCounts {
     counts: SanityCheckDueCounts,
     cards: u32,
     notes: u32,
@@ -165,8 +167,14 @@ struct SanityCheckCounts {
 }
 
 #[derive(Serialize_tuple, Deserialize, Debug)]
-struct SanityCheckDueCounts {
+pub struct SanityCheckDueCounts {
     new: u32,
     learn: u32,
     review: u32,
 }
+
+#[derive(Debug, Default)]
+pub struct FullSyncProgress {
+    transferred_bytes: usize,
+    total_bytes: usize,
+}