diff --git a/Cargo.lock b/Cargo.lock
index aa750753d0..407bbec7c5 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2639,9 +2639,11 @@ dependencies = [
  "parking_lot",
  "roc_can",
  "roc_collections",
+ "roc_fmt",
  "roc_load",
  "roc_module",
  "roc_packaging",
+ "roc_parse",
  "roc_problem",
  "roc_region",
  "roc_reporting",
diff --git a/crates/compiler/region/src/all.rs b/crates/compiler/region/src/all.rs
index c890b20a0a..edcc6f8987 100644
--- a/crates/compiler/region/src/all.rs
+++ b/crates/compiler/region/src/all.rs
@@ -406,6 +406,10 @@ impl LineInfo {
         let end = self.convert_line_column(lc_region.end);
         Region::new(start, end)
     }
+
+    pub fn num_lines(&self) -> u32 {
+        self.line_offsets.len() as u32
+    }
 }
 
 #[test]
diff --git a/crates/lang_srv/Cargo.toml b/crates/lang_srv/Cargo.toml
index 8bdc88d86e..c8cd6b7c1f 100644
--- a/crates/lang_srv/Cargo.toml
+++ b/crates/lang_srv/Cargo.toml
@@ -10,8 +10,10 @@ path = "src/server.rs"
 [dependencies]
 roc_can = { path = "../compiler/can" }
 roc_collections = { path = "../compiler/collections" }
+roc_fmt = { path = "../compiler/fmt" }
 roc_load = { path = "../compiler/load" }
 roc_module = { path = "../compiler/module" }
+roc_parse = { path = "../compiler/parse" }
 roc_problem = { path = "../compiler/problem" }
 roc_region = { path = "../compiler/region" }
 roc_reporting = { path = "../reporting" }
diff --git a/crates/lang_srv/src/analysis.rs b/crates/lang_srv/src/analysis.rs
index d891540a57..67dcd85d5b 100644
--- a/crates/lang_srv/src/analysis.rs
+++ b/crates/lang_srv/src/analysis.rs
@@ -3,16 +3,18 @@ use std::path::{Path, PathBuf};
 use bumpalo::Bump;
 use roc_can::{abilities::AbilitiesStore, expr::Declarations};
 use roc_collections::MutMap;
+use roc_fmt::{Ast, Buf};
 use roc_load::{CheckedModule, LoadedModule};
 use roc_module::symbol::{Interns, ModuleId, Symbol};
 use roc_packaging::cache::{self, RocCacheDir};
-use roc_region::all::{LineInfo, Region};
+use roc_parse::parser::SyntaxError;
+use roc_region::all::LineInfo;
 use roc_reporting::report::RocDocAllocator;
 use roc_solve_problem::TypeError;
 use roc_types::subs::Subs;
 use tower_lsp::lsp_types::{
     Diagnostic, GotoDefinitionResponse, Hover, HoverContents, Location, MarkedString, Position,
-    Range, Url,
+    Range, TextEdit, Url,
 };
 
 use crate::convert::{
@@ -55,6 +57,7 @@ impl GlobalAnalysis {
                 let analyzed_document = AnalyzedDocument {
                     url: source_url,
                     line_info,
+                    source,
                     module: None,
                     diagnostics: all_problems,
                 };
@@ -178,6 +181,7 @@ impl<'a> AnalyzedDocumentBuilder<'a> {
         AnalyzedDocument {
             url: Url::from_file_path(path).unwrap(),
             line_info,
+            source: source.into(),
             module: Some(analyzed_module),
             diagnostics,
         }
@@ -234,6 +238,7 @@ struct AnalyzedModule {
 pub(crate) struct AnalyzedDocument {
     url: Url,
     line_info: LineInfo,
+    source: String,
     module: Option<AnalyzedModule>,
     diagnostics: Vec<Diagnostic>,
 }
@@ -266,6 +271,13 @@ impl AnalyzedDocument {
         }
     }
 
+    fn whole_document_range(&self) -> Range {
+        let line_info = self.line_info();
+        let start = Position::new(0, 0);
+        let end = Position::new(line_info.num_lines(), 0);
+        Range::new(start, end)
+    }
+
     pub fn diagnostics(&mut self) -> Vec<Diagnostic> {
         self.diagnostics.clone()
     }
@@ -320,7 +332,7 @@ impl AnalyzedDocument {
         })
     }
 
-    pub fn goto_definition(&self, symbol: Symbol) -> Option<GotoDefinitionResponse> {
+    pub fn definition(&self, symbol: Symbol) -> Option<GotoDefinitionResponse> {
         let AnalyzedModule { declarations, .. } = self.module()?;
 
         let found_declaration = roc_can::traverse::find_declaration(symbol, declarations)?;
@@ -329,4 +341,44 @@ impl AnalyzedDocument {
 
         Some(GotoDefinitionResponse::Scalar(self.location(range)))
     }
+
+    pub fn format(&self) -> Option<Vec<TextEdit>> {
+        let source = &self.source;
+        let arena = &Bump::new();
+        let ast = parse_all(arena, &self.source).ok()?;
+        let mut buf = Buf::new_in(arena);
+        fmt_all(&mut buf, &ast);
+        let new_source = buf.as_str();
+
+        if source == new_source {
+            None
+        } else {
+            let range = self.whole_document_range();
+            let text_edit = TextEdit::new(range, new_source.to_string());
+            Some(vec![text_edit])
+        }
+    }
+}
+
+fn parse_all<'a>(arena: &'a Bump, src: &'a str) -> Result<Ast<'a>, SyntaxError<'a>> {
+    use roc_parse::{
+        module::{module_defs, parse_header},
+        parser::Parser,
+        state::State,
+    };
+
+    let (module, state) = parse_header(arena, State::new(src.as_bytes()))
+        .map_err(|e| SyntaxError::Header(e.problem))?;
+
+    let (_, defs, _) = module_defs().parse(arena, state, 0).map_err(|(_, e)| e)?;
+
+    Ok(Ast { module, defs })
+}
+
+fn fmt_all<'a>(buf: &mut Buf<'a>, ast: &'a Ast) {
+    roc_fmt::module::fmt_module(buf, &ast.module);
+
+    roc_fmt::def::fmt_defs(buf, &ast.defs, 0);
+
+    buf.fmt_end_of_file();
 }
diff --git a/crates/lang_srv/src/registry.rs b/crates/lang_srv/src/registry.rs
index f6ab506244..c01677ae19 100644
--- a/crates/lang_srv/src/registry.rs
+++ b/crates/lang_srv/src/registry.rs
@@ -1,7 +1,7 @@
 use std::collections::HashMap;
 
 use roc_module::symbol::ModuleId;
-use tower_lsp::lsp_types::{Diagnostic, GotoDefinitionResponse, Hover, Position, Url};
+use tower_lsp::lsp_types::{Diagnostic, GotoDefinitionResponse, Hover, Position, TextEdit, Url};
 
 use crate::analysis::{AnalyzedDocument, GlobalAnalysis};
 
@@ -67,6 +67,11 @@ impl Registry {
     ) -> Option<GotoDefinitionResponse> {
         let symbol = self.document_by_url(url)?.symbol_at(position)?;
         let def_document = self.document_by_module_id(symbol.module_id())?;
-        def_document.goto_definition(symbol)
+        def_document.definition(symbol)
+    }
+
+    pub fn formatting(&mut self, url: &Url) -> Option<Vec<TextEdit>> {
+        let document = self.document_by_url(url)?;
+        document.format()
     }
 }
diff --git a/crates/lang_srv/src/server.rs b/crates/lang_srv/src/server.rs
index 4ddb3de6c6..0babc21812 100644
--- a/crates/lang_srv/src/server.rs
+++ b/crates/lang_srv/src/server.rs
@@ -43,11 +43,17 @@ impl RocLs {
                 work_done_progress: None,
             },
         };
+        let document_formatting_provider = DocumentFormattingOptions {
+            work_done_progress_options: WorkDoneProgressOptions {
+                work_done_progress: None,
+            },
+        };
 
         ServerCapabilities {
             text_document_sync: Some(text_document_sync),
             hover_provider: Some(hover_provider),
             definition_provider: Some(OneOf::Right(definition_provider)),
+            document_formatting_provider: Some(OneOf::Right(document_formatting_provider)),
             ..ServerCapabilities::default()
         }
     }
@@ -146,6 +152,16 @@ impl LanguageServer for RocLs {
                 .goto_definition(&text_document.uri, position)
         })
     }
+
+    async fn formatting(&self, params: DocumentFormattingParams) -> Result<Option<Vec<TextEdit>>> {
+        let DocumentFormattingParams {
+            text_document,
+            options: _,
+            work_done_progress_params: _,
+        } = params;
+
+        panic_wrapper(|| self.registry().formatting(&text_document.uri))
+    }
 }
 
 fn panic_wrapper<T>(f: impl FnOnce() -> Option<T> + std::panic::UnwindSafe) -> Result<Option<T>> {