diff --git a/rebar.config b/rebar.config
index a6475089..1c71a9c0 100644
--- a/rebar.config
+++ b/rebar.config
@@ -1,2 +1,17 @@
 {edoc_opts, [{preprocess, true}]}.
 {erl_opts, [debug_info]}.
+{dialyzer, [
+    {warnings, [
+        unknown,
+        unmatched_returns,
+        error_handling,
+        underspecs
+    ]}
+]}.
+{profiles, [
+    {test, [
+        {dialyzer, [
+            {plt_extra_apps, [eunit]}
+        ]}
+    ]}
+]}.
diff --git a/src/jsx.erl b/src/jsx.erl
index 1b4ceed4..d02d33bd 100644
--- a/src/jsx.erl
+++ b/src/jsx.erl
@@ -54,20 +54,20 @@
 
 -type config() :: jsx_config:config().
 
--spec encode(Source::json_term()) -> json_text().
+-spec encode(Source::json_term()) -> json_text() | {incomplete, encoder()}.
 
 encode(Source) -> encode(Source, []).
 
--spec encode(Source::json_term(), Config::jsx_to_json:config()) -> json_text() | {incomplete, encoder()}.
+-spec encode(Source::json_term(), Config::jsx_config:options()) -> json_text() | {incomplete, encoder()}.
 
 encode(Source, Config) -> jsx_to_json:to_json(Source, Config).
 
 
--spec decode(Source::json_text()) -> json_term().
+-spec decode(Source::json_text()) -> json_term() | {incomplete, decoder()}.
 
 decode(Source) -> decode(Source, []).
 
--spec decode(Source::json_text(), Config::jsx_to_term:config()) -> json_term() | {incomplete, decoder()}.
+-spec decode(Source::json_text(), Config::jsx_config:options()) -> json_term() | {incomplete, decoder()}.
 
 decode(Source, Config) -> jsx_to_term:to_term(Source, Config).
 
@@ -76,7 +76,7 @@ decode(Source, Config) -> jsx_to_term:to_term(Source, Config).
 
 format(Source) -> format(Source, []).
 
--spec format(Source::json_text(), Config::jsx_to_json:config()) -> json_text() | {incomplete, decoder()}.
+-spec format(Source::json_text(), Config::jsx_config:options()) -> json_text().
 
 format(Source, Config) -> jsx_to_json:format(Source, Config).
 
@@ -91,43 +91,44 @@ minify(Source) -> format(Source, []).
 prettify(Source) -> format(Source, [space, {indent, 2}]).
 
 
--spec is_json(Source::any()) -> boolean().
+-spec is_json(Source::binary()) -> boolean() | {incomplete, decoder()}.
 
 is_json(Source) -> is_json(Source, []).
 
--spec is_json(Source::any(), Config::jsx_verify:config()) -> boolean() | {incomplete, decoder()}.
+-spec is_json(Source::binary(), Config::jsx_config:options()) -> boolean() | {incomplete, decoder()}.
 
 is_json(Source, Config) -> jsx_verify:is_json(Source, Config).
 
 
--spec is_term(Source::any()) -> boolean().
+-spec is_term(Source::json_term() | end_stream | end_json) -> boolean() | {incomplete, encoder()}.
 
 is_term(Source) -> is_term(Source, []).
 
--spec is_term(Source::any(), Config::jsx_verify:config()) -> boolean() | {incomplete, encoder()}.
+-spec is_term(Source::json_term() | end_stream | end_json,
+              Config::jsx_config:options()) -> boolean() | {incomplete, encoder()}.
 
 is_term(Source, Config) -> jsx_verify:is_term(Source, Config).
 
 
--spec consult(File::file:name_all()) -> list(json_term()).
+-spec consult(File::file:name_all()) -> list(jsx_consult:json_value()).
 
 consult(File) -> consult(File, []).
 
--spec consult(File::file:name_all(), Config::jsx_to_term:config()) -> list(json_term()).
+-spec consult(File::file:name_all(), Config::jsx_consult:config()) -> list(jsx_consult:json_value()).
 
 consult(File, Config) -> jsx_consult:consult(File, Config).
 
 
 -type decoder() :: fun((json_text() | end_stream | end_json) -> any()).
 
--spec decoder(Handler::module(), State::any(), Config::list()) -> decoder().
+-spec decoder(Handler::module(), State::any(), Config::jsx_config:options()) -> decoder().
 
 decoder(Handler, State, Config) -> jsx_decoder:decoder(Handler, State, Config).
 
 
 -type encoder() :: fun((json_term() | end_stream | end_json) -> any()).
 
--spec encoder(Handler::module(), State::any(), Config::list()) -> encoder().
+-spec encoder(Handler::module(), State::any(), Config::jsx_config:options()) -> encoder().
 
 encoder(Handler, State, Config) -> jsx_encoder:encoder(Handler, State, Config).
 
@@ -156,13 +157,14 @@ encoder(Handler, State, Config) -> jsx_encoder:encoder(Handler, State, Config).
 
 -type parser() :: fun((token() | end_stream) -> any()).
 
--spec parser(Handler::module(), State::any(), Config::list()) -> parser().
+-spec parser(Handler::module(), State::any(), Config::jsx_config:options()) -> parser().
 
 parser(Handler, State, Config) -> jsx_parser:parser(Handler, State, Config).
 
 -opaque internal_state() :: tuple().
 
--spec resume(Term::json_text() | token(), InternalState::internal_state(), Config::list()) -> any().
+-spec resume(Term::json_text() | token(), InternalState::internal_state(),
+             Config::jsx_config:options()) -> jsx:decoder() | {incomplete, jsx:decoder()}.
 
 resume(Term, {decoder, State, Handler, Acc, Stack}, Config) ->
     jsx_decoder:resume(Term, State, Handler, Acc, Stack, jsx_config:parse_config(Config));
diff --git a/src/jsx_config.erl b/src/jsx_config.erl
index 47cbcf72..ba1d872a 100644
--- a/src/jsx_config.erl
+++ b/src/jsx_config.erl
@@ -49,8 +49,55 @@
 -type config() :: #config{}.
 -export_type([config/0]).
 
+-type option() :: valid_flag()
+                | {valid_flag(), boolean()}
+                | {strict, [strict_option()]}
+                | {error_handler, fun((any(), any(), any()) -> ok)}
+                | {incomplete_handler, fun((any(), any(), any()) -> ok)}
+                | {return_maps, boolean()}
+                | {labels, label_option()}
+                | {space, non_neg_integer()}
+                | {indent, non_neg_integer()}
+                | {depth, non_neg_integer()}
+                | {newline, binary()}
+                | legacy_option()
+                | {legacy_option(), boolean()}.
+-type legacy_option() :: strict_comments
+                       | strict_commas
+                       | strict_utf8
+                       | strict_single_quotes
+                       | strict_escapes
+                       | strict_control_codes.
+
+-type options() :: [option()].
+-export_type([options/0]).
+
+-type strict_option() :: comments
+                       | trailing_commas
+                       | utf8
+                       | single_quotes
+                       | escapes
+                       | control_codes.
+-type label_option() :: binary
+                      | atom
+                      | existing_atom
+                      | attempt_atom.
+
+-type valid_flag() :: escaped_forward_slashes
+                    | escaped_strings
+                    | unescaped_jsonp
+                    | dirty_strings
+                    | multi_term
+                    | return_tail
+                    | repeat_keys
+                    | strict
+                    | stream
+                    | uescape
+                    | error_handler
+                    | incomplete_handler.
+
 %% parsing of jsx config
--spec parse_config(Config::proplists:proplist()) -> config().
+-spec parse_config(Config::options()) -> config().
 
 parse_config(Config) -> parse_config(Config, #config{}).
 
@@ -116,7 +163,7 @@ parse_strict(_Strict, _Rest, _Config) ->
 
 
 
--spec config_to_list(Config::config()) -> proplists:proplist().
+-spec config_to_list(Config::config()) -> options().
 
 config_to_list(Config) ->
     reduce_config(lists:map(
@@ -153,7 +200,7 @@ reduce_config([Else|Input], Output, Strict) ->
     reduce_config(Input, [Else] ++ Output, Strict).
 
 
--spec valid_flags() -> [atom()].
+-spec valid_flags() -> [valid_flag(), ...].
 
 valid_flags() ->
     [
@@ -172,7 +219,7 @@ valid_flags() ->
     ].
 
 
--spec extract_config(Config::proplists:proplist()) -> proplists:proplist().
+-spec extract_config(Config::options()) -> options().
 
 extract_config(Config) ->
     extract_parser_config(Config, []).
diff --git a/src/jsx_consult.erl b/src/jsx_consult.erl
index d25306ab..e0e73c97 100644
--- a/src/jsx_consult.erl
+++ b/src/jsx_consult.erl
@@ -32,7 +32,7 @@
     return_maps = false
 }).
 
--type config() :: list().
+-type config() :: proplists:proplist().
 -export_type([config/0]).
 
 -type json_value() :: list(json_value())
@@ -43,6 +43,7 @@
     | integer()
     | float()
     | binary().
+-export_type([json_value/0]).
 
 opts(Opts) -> [return_maps, multi_term] ++ Opts.
 
@@ -61,8 +62,8 @@ consult(File, Config) when is_list(Config) ->
     end.
 
 
--type state() :: {[], proplists:proplist(), {list(), #config{}}}.
--spec init(Config::proplists:proplist()) -> state().
+-type state() :: {[], config(), {list(), #config{}}}.
+-spec init(Config::config()) -> state().
 
 init(Config) -> {[], Config, jsx_to_term:start_term(Config)}.
 
diff --git a/src/jsx_decoder.erl b/src/jsx_decoder.erl
index 7d92c0d1..a706c891 100644
--- a/src/jsx_decoder.erl
+++ b/src/jsx_decoder.erl
@@ -32,7 +32,7 @@
 -export([decoder/3, resume/6]).
 
 
--spec decoder(Handler::module(), State::any(), Config::list()) -> jsx:decoder().
+-spec decoder(Handler::module(), State::any(), Config::jsx_config:options()) -> jsx:decoder().
 
 decoder(Handler, State, Config) ->
     fun(JSON) -> start(JSON, {Handler, Handler:init(State)}, [], jsx_config:parse_config(Config)) end.
diff --git a/src/jsx_encoder.erl b/src/jsx_encoder.erl
index c6db8efb..a1242a79 100644
--- a/src/jsx_encoder.erl
+++ b/src/jsx_encoder.erl
@@ -25,19 +25,19 @@
 
 -export([encoder/3, encode/1, encode/2]).
 
--spec encoder(Handler::module(), State::any(), Config::list()) -> jsx:encoder().
+-spec encoder(Handler::module(), State::any(), Config::jsx_config:options()) -> jsx:encoder().
 
 encoder(Handler, State, Config) ->
     Parser = jsx:parser(Handler, State, Config),
     fun(Term) -> Parser(encode(Term) ++ [end_json]) end.
 
 
--spec encode(Term::any()) -> any().
+-spec encode(Term::any()) -> [any(), ...].
 
 encode(Term) -> encode(Term, ?MODULE).
 
 
--spec encode(Term::any(), EntryPoint::module()) -> any().
+-spec encode(Term::any(), EntryPoint::module()) -> [any(), ...].
 
 encode(Map, _EntryPoint) when is_map(Map), map_size(Map) < 1 ->
     [start_object, end_object];
diff --git a/src/jsx_parser.erl b/src/jsx_parser.erl
index 070c9344..8506b037 100644
--- a/src/jsx_parser.erl
+++ b/src/jsx_parser.erl
@@ -27,7 +27,7 @@
 -export([init/1, handle_event/2]).
 
 
--spec parser(Handler::module(), State::any(), Config::list()) -> jsx:parser().
+-spec parser(Handler::module(), State::any(), Config::jsx_config:options()) -> jsx:parser().
 
 parser(Handler, State, Config) ->
     fun(Tokens) -> value(Tokens, {Handler, Handler:init(State)}, [], jsx_config:parse_config(Config)) end.
@@ -630,7 +630,7 @@ to_hex(X) -> X + 48.    %% ascii "1" is [49], "2" is [50], etc...
 
 
 %% for raw input
--spec init(proplists:proplist()) -> list().
+-spec init([]) -> [].
 
 init([]) -> [].
 
diff --git a/src/jsx_to_json.erl b/src/jsx_to_json.erl
index fb14df3d..d20add61 100644
--- a/src/jsx_to_json.erl
+++ b/src/jsx_to_json.erl
@@ -36,17 +36,16 @@
     newline = <<$\n>>
 }).
 
--type config() :: list().
--export_type([config/0]).
+-type config() :: proplists:proplist().
 
 
--spec to_json(Source::any(), Config::config()) -> binary().
+-spec to_json(Source::jsx:json_term(), Config::jsx_config:options()) -> binary().
 
 to_json(Source, Config) when is_list(Config) ->
     (jsx:encoder(?MODULE, Config, jsx_config:extract_config(Config ++ [escaped_strings])))(Source).
 
 
--spec format(Source::binary(), Config::config()) -> binary().
+-spec format(Source::binary(), Config::jsx_config:options()) -> jsx:json_text().
 
 format(Source, Config) when is_binary(Source) andalso is_list(Config) ->
     (jsx:decoder(?MODULE, Config, jsx_config:extract_config(Config ++ [escaped_strings])))(Source);
@@ -91,7 +90,7 @@ parse_config([], Config) ->
 
 
 -type state() :: {unicode:charlist(), #config{}}.
--spec init(Config::proplists:proplist()) -> state().
+-spec init(Config::config()) -> state().
 
 init(Config) -> {[], parse_config(Config)}.
 
@@ -390,7 +389,7 @@ custom_newline_test_() ->
     [
         {"single key object", ?_assert(
             jsx:format(<<"{\"k\":\"v\"}">>, [space, {indent, 2}, {newline, <<$\r>>}]) 
-                =:= <<"{\r  \"k\": \"v\"\r}">>)
+                =:= <<"{\r  \"k\": \"v\"\r}">>) 
         }
     ].
 
diff --git a/src/jsx_to_term.erl b/src/jsx_to_term.erl
index e3c99e7c..07beba4d 100644
--- a/src/jsx_to_term.erl
+++ b/src/jsx_to_term.erl
@@ -41,21 +41,9 @@
     return_maps = false
 }).
 
--type config() :: list().
--export_type([config/0]).
-
--type json_value() :: list(json_value())
-    | list({binary() | atom(), json_value()}) | [{},...]
-    | {with_tail, json_value(), binary()}
-    | map()
-    | true
-    | false
-    | null
-    | integer()
-    | float()
-    | binary().
-
--spec to_term(Source::binary(), Config::config()) -> json_value().
+-type config() :: proplists:proplist().
+
+-spec to_term(Source::binary(), Config::jsx_config:options()) -> jsx:json_term() | {incomplete, jsx:decoder()}.
 
 to_term(Source, Config) when is_list(Config) ->
     (jsx:decoder(?MODULE, [return_maps] ++ Config, jsx_config:extract_config(Config)))(Source).
@@ -87,7 +75,7 @@ parse_config([], Config) ->
 
 
 -type state() :: {list(), #config{}}.
--spec init(Config::proplists:proplist()) -> state().
+-spec init(Config::config()) -> state().
 
 init(Config) -> start_term(Config).
 
diff --git a/src/jsx_verify.erl b/src/jsx_verify.erl
index 5f4a3d89..5eef4d29 100644
--- a/src/jsx_verify.erl
+++ b/src/jsx_verify.erl
@@ -26,8 +26,9 @@
 -export([is_json/2, is_term/2]).
 -export([init/1, handle_event/2]).
 
+-type config() :: proplists:proplist().
 
--spec is_json(Source::binary(), Config::proplists:proplist()) -> true | false | {incomplete, jsx:decoder()}.
+-spec is_json(Source::binary(), Config::jsx_config:options()) -> true | false | {incomplete, jsx:decoder()}.
 
 is_json(Source, Config) when is_list(Config) ->
     try (jsx:decoder(?MODULE, Config, jsx_config:extract_config(Config)))(Source)
@@ -35,7 +36,8 @@ is_json(Source, Config) when is_list(Config) ->
     end.
 
 
--spec is_term(Source::any(), Config::proplists:proplist()) -> true | false | {incomplete, jsx:encoder()}.
+-spec is_term(Source::jsx:json_term() | end_stream | end_json,
+              Config::jsx_config:options()) -> true | false | {incomplete, jsx:encoder()}.
 
 is_term(Source, Config) when is_list(Config) ->
     try (jsx:encoder(?MODULE, Config, jsx_config:extract_config(Config)))(Source)
@@ -68,7 +70,7 @@ parse_config([], Config) ->
 
 %% we don't actually need any state for this
 -type state() :: [].
--spec init(Config::proplists:proplist()) -> state().
+-spec init(Config::config()) -> state().
 
 init(Config) -> parse_config(Config).