diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index 0ade010..5587324 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -40,10 +40,13 @@ jobs:
           arch: ${{ matrix.arch }}
       - uses: julia-actions/julia-buildpkg@v1
       - uses: julia-actions/julia-runtest@v1
+        env:
+          JULIA_COVERAGE_BLACK_HOLE_SERVER_URL_PUT: https://httpbingo.julialang.org/put
       # submit coverage data to a black hole server, and collect new coverage data on that
       - run: julia --color=yes --project=. --code-coverage=user etc/travis-coverage.jl
         working-directory: ${{ github.workspace }}
         env:
+          JULIA_COVERAGE_IS_BLACK_HOLE_SERVER: true
           COVERALLS_TOKEN: token
           COVERALLS_URL: https://httpbingo.julialang.org/post
           CODECOV_URL: https://httpbingo.julialang.org
diff --git a/Project.toml b/Project.toml
index a655fb5..9b00fbe 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,7 +1,7 @@
 name = "Coverage"
 uuid = "a2441757-f6aa-5fb2-8edb-039e3f45d037"
 authors = ["Iain Dunning <iaindunning@gmail.com>", "contributors"]
-version = "1.2.2"
+version = "1.3.0"
 
 [deps]
 CoverageTools = "c36e975a-824b-4404-a568-ef97ca766997"
@@ -18,7 +18,8 @@ MbedTLS = "0.6, 0.7, 1"
 julia = "1"
 
 [extras]
+CoverageTools = "c36e975a-824b-4404-a568-ef97ca766997"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [targets]
-test = ["Test"]
+test = ["CoverageTools", "Test"]
diff --git a/src/codecovio.jl b/src/codecovio.jl
index a28496d..a8a8d50 100644
--- a/src/codecovio.jl
+++ b/src/codecovio.jl
@@ -223,14 +223,28 @@ module Codecov
         @info "Submitting data to Codecov..."
         @debug "Codecov.io API URL:\n" * mask_token(uri_str)
 
+        is_black_hole_server = parse(Bool, strip(get(ENV, "JULIA_COVERAGE_IS_BLACK_HOLE_SERVER", "false")))::Bool
         if !dry_run
-            heads   = Dict("Content-Type" => "application/json")
-            data    = to_json(fcs)
-            req     = HTTP.post(uri_str; body = JSON.json(data), headers = heads)
-            @debug "Result of submission:" * mask_token(String(req))
+            # Tell Codecov we have an upload for them
+            response = HTTP.post(uri_str; headers=Dict("Accept" => "text/plain"))
+            # Get the temporary URL to use for uploading to S3
+            repr = String(response)
+            s3url = get(split(String(response.body), '\n'), 2, "")
+            repr = chomp(replace(repr, s3url => ""))
+            @debug "Result of submission:" * repr
+            !is_black_hole_server && upload_to_s3(; s3url=s3url, fcs=fcs)
         end
     end
 
+    function upload_to_s3(; s3url, fcs)
+        startswith(s3url, "https://") || error("Invalid codecov response: $s3url")
+        # Upload to S3
+        request = HTTP.put(s3url; body=json(to_json(fcs)),
+                           header=Dict("Content-Type" => "application/json",
+                                       "x-amz-storage-class" => "REDUCED_REDUNDANCY"))
+        @debug "Result of submission:" * mask_token(String(request))
+    end
+
     function construct_uri_string(kwargs::Dict)
         url = get(ENV, "CODECOV_URL", "")
         isempty(url) || (kwargs = set_defaults(kwargs, codecov_url = url))
@@ -252,7 +266,7 @@ module Codecov
             error("the codecov_url should not end with a /, given url $(repr(codecov_url))")
         end
 
-        codecov_url_path = get(kwargs, :codecov_url_path, "/upload/v2")
+        codecov_url_path = get(kwargs, :codecov_url_path, "/upload/v4")
         if isempty(codecov_url_path) || codecov_url_path[1] != '/' || codecov_url_path[end] == '/'
             error("the codecov_url_path should begin with, but not end with, a /, given url $(repr(codecov_url_path))")
         end
diff --git a/test/runtests.jl b/test/runtests.jl
index 1b4ede7..86129c4 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -6,6 +6,8 @@
 
 using Coverage, Test, LibGit2
 
+import CoverageTools
+
 @testset "Coverage" begin
 # set up base system ENV vars for testing
 withenv(
@@ -430,11 +432,22 @@ withenv(
 
         # in the case above, the token is at the end. Let's test explicitly,
         # that this also works if the token occurs earlier in the url
-        url = "https://enterprise-codecov-1.com/upload/v2?token=token_name_1&build=t_job_num"
+        url = "https://enterprise-codecov-1.com/upload/v4?token=token_name_1&build=t_job_num"
         masked = Coverage.Codecov.mask_token(url)
-        @test masked == "https://enterprise-codecov-1.com/upload/v2?token=<HIDDEN>&build=t_job_num"
+        @test masked == "https://enterprise-codecov-1.com/upload/v4?token=<HIDDEN>&build=t_job_num"
+
+        @testset "Run the `Coverage.Codecov.upload_to_s3` function against the \"black hole\" server" begin
+            black_hole_server = get(
+                ENV,
+                "JULIA_COVERAGE_BLACK_HOLE_SERVER_URL_PUT",
+                "https://httpbingo.julialang.org/put",
+            )
+            s3url = black_hole_server
+            fcs = Vector{CoverageTools.FileCoverage}(undef, 0)
+            Coverage.Codecov.upload_to_s3(; s3url=s3url, fcs=fcs)
+        end
     end
-            
+
 
     @testset "coveralls" begin
         # NOTE: this only returns actual content if this package is devved.