Useful tools for working with HTTP organised by HTTP verbs (GET(), POST(), etc). Configuration functions make it easy to control additional request components (authenticate(), add_headers() and so on).
The aim of httr is to provide a wrapper for the curl package, customised to the demands of modern web APIs.
Functions for the most important http verbs:
Automatic connection sharing across requests to the same website (by default, curl handles are managed automatically), cookies are maintained across requests, and a up-to-date root-level SSL certificate store is used.
Requests return a standard reponse object that captures the http status line, headers and body, along with other useful information.
Response content is available with
content() as a raw vector (
as = "raw"), a character vector (
as = "text"), or parsed into an R object
as = "parsed"), currently for html, xml, json, png and jpeg.
You can convert http errors into R errors with
Config functions make it easier to modify the request in common ways:
Support for OAuth 1.0 and 2.0 with
The demo directory has eight OAuth demos: four for 1.0 (twitter, vimeo,
withings and yahoo) and four for 2.0 (facebook, github, google, linkedin).
OAuth credentials are automatically cached within a project.
To get the current released version from CRAN:
To get the current development version from github:
safe_callback() has been removed.
is_interactive argument to
oauth_listener() has been deprecated, as the R session does not actually
need to be interactive.
get_callback() set and query callback functions
that are called right before and after performing an HTTP request
RETRY() now retries if an error occurs during the request (@asieira, #404),
and gains two new arguments:
terminate_on gives you greater control over which status codes should
it stop retrying. (@asieira, #404)
pause_min allows for sub-second delays. (Use with caution! Generally the
default is preferred.) (@r2evans)
If the server returns HTTP status code 429 and specifies a
value, that value will now be used instead of exponential backoff with
jitter, unless it's smaller than
pause_min. (@nielsoledam, #472)
New oauth cache files are always added to
.gitignore and, if it exists,
.Rbuildignore. Specifically, this now happens when option
httr_oauth_cache = TRUE or user specifies cache file name explicitly.
oauth_encode() now handles UTF-8 characters correctly.
oauth_app() allows you to specify the
redirect_url if you need to
oauth_service_token() gains a
sub parameter so you can request
access on behalf of another user (#410), and accepts a character vector
scopes as was described in the documentation (#389).
oauth_signature() now normalises the URL as described in the OAuth1.0a
spec (@leeper, #435)
pull out parts of the OAuth process for reuse elsewhere (#457).
oauth2.0_token() gains three new arguments:
config_init allows you to supply additional config for the initial
request. This is needed for some APIs (e.g. reddit) which rate limit
user_agent (@muschellij2, #363).
client_credentials, allows you to use the OAauth2 Client Credential
Grant. See RFC 6749
for details. (@cderv, #384)
credentials argument that allows you to customise the auth flow.
For advanced used only (#457)
is_interactive argument to
oauth_listener() has been deprecated, as the R session does not need
to be interactive.
BROWSER() prints a message telling you to browse to the URL if called
in a non-interactive session.
find_cert_bundle() will now correctly find cert bundle in "R_HOME/etc"
You can now send lists containing
curl::form_data() in the
requests with `encoding = "multipart". This makes it possible to specify the
mime-type of individual components (#430).
modify_url() recognises more forms of empty queries. This eliminates a
source of spurious trailing
?= (@jennybc, #452).
length() method of the internal
path class is no longer exported
oauth_signature() no longer prepends 'oauth_' to additional parameters.
print() methods now invisibly return
DELETE() gains a body parameter (#326).
encode = "raw" allows you to do your own encoding for requests with
http_type() returns the content/mime type of a request, sans parameters.
No longer uses use custom requests for standard
POST requests (#356,
#357). This has the side-effect of properly following redirects after
POST, fixing some login issues (eg hadley/rvest#133).
multipart argument to
has been removed.
The cross-session OAuth cache is now created with permission 0600, and should give a better error if it can't be created (#365).
RETRY() function allows you to retry a request multiple times until
it succeeds (#353).
The default user agent string is now computed once and cached. This is a small performance improvement, but important for local connections (#322, @richfitz).
oauth_callback() gains trailing slash for facebook compatibility (#324).
con argument to control where progress bar is rendered
use_basic_auth option is used to obtain a token, token refreshes
will now use basic authentication too.
Suppress unhelpful "No encoding supplied: defaulting to UTF-8." when printing a response (#327).
All auto parser functions now have consistent arguments. This fixes problem
... is pass on to another function (#330).
parse_media() can once again parse multiple parameters (#362, #366).
Fix in readfunction to close connection when done.
warn_for_status() and (new)
message argument with new
task argument that optionally describes
the current task. This allows API wrappers to provide more informative
error messages on failure (#277, #302).
warn_for_status() return the response if there were no errors. This
makes them easier to use in pipelines (#278).
url_successful() have been deprecated in favour of the more
http_error(), which works with urls, responses and integer status
oauth1.0_token() gains RSA-SHA1 signature support with the
argument (@nathangoulding, #316).
oauth2.0_token() throws an error if it fails to get an access token (#250)
and gains two new arguments:
user_params allows you to pass arbitrary additional parameters to the
token access endpoint when acquiring or refreshing a token
use_basic_auth allows you to pick use http authentication when
getting a token (#310, @grahamrp).
oauth_service_token() checks that its arguments are the correct types
(#282) and anways returns a
request object (#313, @nathangoulding).
refresh_oauth2.0() checks for known OAuth2.0 errors and clears the
locally cached token in the presense of any (@nathangoulding, #315).
httr no longer bundles
cacert.pem, and instead it relies on the bundle in
openssl. This bundle is only used a last-resort on windows with R <3.2.0.
Switch to 'openssl' package for hashing, hmac, signatures, and base64.
httr no longer depends on stringr (#285, @jimhester).
build_url() collapses vector
/ (#280, @artemklevtsov).
content(x) uses xml2 for XML documents and readr for csv and tsv.
content(, type = "text") defaults to UTF-8 encoding if not otherwise
has_content() correctly tests for the presence/absence of body content (#91).
parse_url() correctly parses urls like
file:///a/b/c work (#309).
TRUE to fix for 'progress callback must return boolean'
warning (@jeroenooms, #252).
upload_file() supports very large files (> 2.5 Gb) (@jeroenooms, #257).
httr no longer uses the RCurl package. Instead it uses the curl package, a modern binding to libcurl written by Jeroen Ooms (#172). This should make httr more reliable and prevent the "easy handle already used in multi handle" error. This change shouldn't affect any code that uses httr - all the changes have happened behind the scenes.
oauth_listener can now listen on a custom IP address and port (the
previously hardwired ip:port of
127.0.0.1:1410 is now just the default).
This permits authentication to work under other settings, such as inside
docker containers (which require localhost uses
0.0.0.0 instead). To
configure, set the system environmental variables
HTTR_PORT respectively (@cboettig, #211).
POST(encode = 'json') now automatically turns length-1 vectors into json
scalars. To prevent this automatic "unboxing", wrap the vector in
PATCH() now drop
NULL body elements. This is
convenient and consistent with the behaviour for url query params.
cookies argument to
handle() is deprecated - cookies are always
turned on by default.
brew_dr() has been renamed to
httr_dr() - that's what it should've
been in the first place!
content(type = "text") compares encodings in a case-insensitive manner
context(type = "auto") uses a better strategy for text based formats (#209).
This should allow the
encoding argument to work more reliably.
config() now cleans up duplicated options (#213).
CURL_CA_BUNDLE environment variable to look for cert bundle on
safe_callback() is deprecated - it's no longer needed with curl.
PUT() now clean up after themselves when uploading a single
proxy() gains an
auth argument which allows you to pick the type of
http authentication used by the proxy (#216).
encode arguments so you can generate
arbitrary requests with a body.
tumblr added as an
Correctly parse headers with multiple
:, thanks to @mmorgan (#180).
content(), if no type is provided to function or specified in headers,
and we can't guess the type from the extension, we now assume that it's
Throw error if
timeout() is less than 1 ms (#175).
Improved LinkedIn OAuth demo (#173).
write_stream() allows you to process the response from a server as
a stream of raw vectors (#143).
Suport for Google OAuth2 service accounts. (#119, thanks to help from @siddharthab).
VERB() allows to you use custom http verbs (#169).
handle_reset() to allow you to reset the handle if you get the error
"easy handle already used in multi handle" (#112).
Uses R6 instead of RC. This makes it possible to extend the OAuth classes from outside of httr (#113).
Now only set
capath on Windows - system defaults on linux and mac ox
seem to be adequate (and in some cases better). I've added a couple of tests
to ensure that this continues to work in the future.
vignette("api-packages") gains more detailed instructions on
setting environment variables, thanks to @jennybc.
revoke_all() to revoke all stored tokens (if possible) (#77).
Fix for OAuth 2 process when using
options(httr_oob_default = TRUE)
brew_dr() checks for common problems. Currently checks if your libCurl
uses NSS. This is unlikely to work so it gives you some advice on how to
fix the problem (thanks to @eddelbuettel for debugging this problem).
Content-Type set to title case to avoid errors in servers which do not
correctly implement case insensitivity in header names. (#142, #146) thanks
to Håkon Malmedal (@hmalmedal) and Jim Hester (@jimhester).
Correctly parse http status when it only contains two components (#162).
Correctly parse http headers when field name is followed by any amount (including none) of white space.
Default "Accepts" header set to
application/json, text/xml, application/xml, */*: this should slightly
increase the likelihood of getting xml back.
application/xml is correctly
converted to text before being parsed to
Make it again possible to override the content type set up by
when sending data (#140).
safe_callback() function operator that makes R functions safe for
use as RCurl callbacks (#144).
Added support for passing oauth1 tokens in URL instead of the headers (#145, @bogstag).
Default to out-of-band credential exchange when
httpuv isn't installed.
new_token() has been removed - this was always an internal function
so you should never have been using it. If you were, switch to creating
the tokens directly.
guess_media(), and instead use
You can now save response bodies directly to disk by using the
config. This is useful if you want to capture large files that don't fit in
Default accept header is now "application/json, text/xml, /" - this should encourage servers to send json or xml if they know how.
httr_options() allows you to easily filter the options, e.g.
POST() now specifies Curl options more precisely so that Curl know's
that you're doing a POST and can respond appropriately to redirects.
Preliminary and experimental support for caching with
rerequest() (#129). Be aware that this API is likely to change in
parse_http_date() parses http dates according RFC2616 spec.
Requests now print the time they were made.
application/xml is automatically parsed with ``XML::xmlParse()`.
Now possible to specify both handle and url when making a request.
content(type = "text") uses
readBin() instead of
that strings with embedded NULLs (e.g. WINDOWS-1252) can be re-encoded
DELETE() now returns body of request (#138).
headers() is now a generic with a method for response objects.
parse_media() failed to take into account that media types are
case-insenstive - this lead to bad re-encoding for content-types like
Typo which broke
set_cookies() fixed by @hrbrmstr.
url_ok() works correctly now, instead of always returning
a bug since version 0.4 (#133).
Remove redundant arguments
simplifyMatrix for json parser.
cookies() functions to extract headers and cookies
from responses. Previoulsy internal
status_code() function now exported
status_code() from responses.
PATCH() now use
encode argument to determine how
list inputs are encoded. Valid values are "multiple", "form" or "json".
multipart argument is now deprecated (#103). You can stream a single
file from disk with
upload_file("path/"). The mime type will be guessed
from the extension, or can be supplied explicitly as the second argument to
progress() will display a progress bar, useful if you're doing large
uploads or downloads (#17).
verbose() now uses a custom debug function so that you can see exactly
what data is sent to the server. Arguments control exactly what is included,
and the defaults have been selected to be more helpful for the most common
with_verbose() makes it easier to see verbose information when http
requests are made within other functions (#87).
quickstart vignette to help you get up and running with httr.
api-packages vignette describes how best practices to follow when
writing R packages that wrap web APIs.
httr_options() lists all known config options, translating between
their short R names and the full libcurl names. The
function allows you to jump directly to the online documentation for an
authenticate() now defaults to
type = "basic" which is pretty much the
only type of authentication anyone uses.
cacert.pem to version at 2014-04-22 (#114).
content_type_json() make it
easier to set the content type for
POST requests (and other requests with
has_content() tells you if request has any content associated with it (#91).
is_interactive() parameter to
oauth_header() now exported to make it easier to
construct custom authentication for APIs that use only some components of
the full OAuth process (e.g. 2 legged OAuth).
query parameters are now dropped automatically.
print()ing a response, httr will only attempt to print the first few
lines if it's a text format (i.e. either the main type is text or is
application/json). It will also truncate each line so that it fits on
screen - this should hopefully make it easier to see a little bit of the
content, without filling the screen with gibberish.
new_bin() has been removed: it's easier to see what's going on in
user_agent() once again overrides default (closes #97)
parse(type = "auto") returns NULL if no content associated with request
Better strategy for resetting Curl handles prevents carry-over of error status and other problems (#112).
with_config() now work with
OAuth 2.0 has recieved a major overhaul in this version. The authentication dance now works in more environments (including RStudio), and is generally a little faster. When working on a remote server, or if R's internet connection is constrained in other ways, you can now use out-of-band authentication, copying and pasting from any browser to your R session. OAuth tokens from endpoints that regularly expire access tokens can now be refreshed, and will be refresh automatically on authentication failure.
httr now uses project (working directory) based caching: every time you
create or refresh a token, a copy of the credentials will be saved in
.httr-oauth. You can override this default for individual tokens with the
cache parameter, or globally with the
httr_oauth_cache option. Supply
either a logical vector (
TRUE = always cache,
FALSE = never cache,
NA = ask), or a string (the path to the cache file).
You should NOT include this cache file in source code control - if you do,
delete it, and reset your access token through the corresponding web interface.
To help, httr will automatically add appropriate entries to
These changes mean that you should only ever have to authenticate once per project, and you can authenticate from any environment in which you can run R. A big thanks go to Craig Citro (@craigcitro) from google, who contributed much code and many ideas to make this possible.
The OAuth token objects are now reference classes, which mean they can be
updated in place, such as when an access token expires and needs to be
refreshed. You can manually refresh by calling
$refresh() on the object.
You can force reinitialisation (to do the complete dance from
scratch) by calling
$reinit(force = TRUE).
If a signed OAuth2 request fails with a 401 and the credentials have a
refresh_token, then the OAuth token will be automatically refreshed (#74).
OAuth tokens are cached locally in a file called
you opt out). This file should not be included in source code control,
and httr will automatically add to
The caching policy is described in more detail in the help for the
The OAuth2 dance can now be performed without running a local webserver
(#33, thanks to @craigcitro). To make that the default, set
options(httr_oob_default = TRUE). This is useful when running R remotely.
Add support for passing oauth2 tokens in headers instead of the URL, and make this the default (#34, thanks to @craigcitro).
OAuth endpoints can store arbitrary extra urls.
Use the httpuv webserver for the OAuth dance instead of the built-in httpd server (#32, thanks to @jdeboer). This makes the dance work in Rstudio, and also seems a little faster. Rook is no longer required.
oauth_endpoints() includes some popular OAuth endpoints.
HTTP verbs (
POST() etc) now pass unnamed arguments to
and named arguments to
The placement of
PUT() has been tweaked
so that you must always specify
multipart arguments with their
full name. This has always been recommended practice; now it is enforced.
httr includes its own copy of
cacert.pem, which is more recent than
the version included in RCurl (#67).
Added default user agent which includes versions of Curl, RCurl and httr.
Switched to jsonlite from rjson.
Content parsers no longer load packages on to search path.
stop_for_status() now raises errors with useful classes so that you can
tryCatch() to take different actions depending on the type of error.
http_condition() for more details.
httr now imports the methods package so that it works when called with Rscript.
New automatic parsers for mime types
Add support for
fragment in url building/parsing (#70, thanks to
You can suppress the body entirely in
body = FALSE.
If you supply multiple headers of the same name, the value of the most recently set header will always be used.
Urls with missing query param values (e.g.
http://x.com/?q=) are now
parsed correctly (#27). The names of query params are now also escaped
and unescaped correctly when parsing and building urls.
Default html parser is now
XML::htmlParse() which is easier to use
with xpath (#66).
OAuth now uses custom escaping function which is guaranteed to work on all platforms (Fixes #21)
When concatenating configs, concatenate all the headers. (Fixes #19)
hmac_sha1 since so many authentication protocols need this
content will automatically guess what type of output (parsed, text or raw)
based on the content-type header. It also automatically converts text
content to UTF-8 (using the charset in the media type) and can guess at mime
type from extension if server doesn't supply one. Media type and encoding
can be overridden with the
encoding arguments respectively.
response objects automatically print content type to aid debugging.
text_content has become
context(, "text") and
content(, "parsed"). The previous calls are deprecated and will be removed
in a future version.
oauth_listener, use existing httpd port if help server has already been
started. This allows the ouath authentication dance to work if you're in
RStudio. (Fixes #15).
add several functions related to checking the status of an http request.
Those are :
url_success as well as
build_url: correctly add params back into full url.
Add new default config: use the standard SSL certificate
Add recommendation to use custom handles with