curl user survey analysis 2025

Version: 1.0

Daniel Stenberg, July 3, 2025

About curl

curl is an established and mature open source project that produces the curl tool and the libcurl library among other things. While a small project, with just a few maintainers, its products run in many billions of Internet connected devices, applications, tools, games and services. curl is one of the world’s most widely used software components.

curl was first released in March 1998, building on its predecessors originating back to November 1996.

To remain relevant and to maintain a place in people’s toolboxes, curl must keep up. Keep up with what users want, with how internet transfers are done, with Internet standards and with protocol development.

About the survey

Background

curl features no telemetry, and the curl website has no logs and no tracking. Most users even download and install curl from elsewhere and not directly from us. In order to get proper feedback and get a feel for what users think, asking questions like this is the only viable way.

We run a curl user survey annually in an attempt to catch trends, views and long term changes in the project, its users, its surrounding and in how curl fits into the wider ecosystem. This year, the survey was up 14 days from May 19 to and including June 1. This was the 12th annual survey.

The survey was announced on the curl-users and curl-library mailing lists (with reminders), numerous times on Daniel’s Mastodon (@bagder@mastodon.social) on LinkedIn and on Daniel’s blog (https://daniel.haxx.se/blog). The survey was also announced on the curl web site at the top of most pages on the site that made it hard to miss for visitors.

Bias

We only reach and get responses from a small subset of users who voluntarily decide to fill in the questionnaire while the vast majority of users and curl developers never get to hear about it and never get an opportunity to respond. Self-selected respondents to a survey makes the results hard to interpret and judge. This should make us ask ourselves: is this what our users think, or is it just the opinions of the tiny subset of users that we happened to reach this year. We simply have to work with what we have.

Many statements listed in this survey analysis are verbatim quotes from respondents. We in the curl project do not necessarily agree with those or think the same way. Some might even be downright offensive. Beware.

Stability

For several years we have witnessed how the responses to the surveys are strikingly similar year-to-year even while the majority of the people who respond say they did not answer the survey the previous year. It might imply that the responses are indicative for a wider population.

Hosting

We use a service run by Google to perform the survey, which leads to us losing the share of users who refuse to use services hosted by them. We feel compelled to go with simplicity, no cost and convenience of the service rather than trying to please everyone. We have simply not put in the effort to switch to an alternative provider for the survey.

Analysis

This analysis is now for the first time done entirely using markdown, perl scripts and gnuplot, with conversions to HTML and pdf using pandoc. This should hopefully make it easier and quicker to repeat this work in the coming years. We can also easily do updates, fix typos etc since everything is in git.

You may also notice that this year I have included the year 2025 in many image titles and a semi-transparent curl logo symbol in the graphs. This, to make sure that the images don’t lose that context if they are copied and shared elsewhere.

10 take-aways

  1. Linux is the primary curl platform
  2. HTTPS and HTTP remain the most used protocols
  3. Windows 11 is the most used Windows version people run curl on
  4. 32 bit x86 is used by just 7% of the users running curl on Windows
  5. all supported protocols are used by at least some users
  6. OpenSSL remain the most used TLS backend
  7. libssh2 is the most used SSH backend
  8. 85% of respondents scored curl 5 out of 5 for “security handling”
  9. Mastodon is a popular communication channel, and is wanted more
  10. The median used curl version is just one version away from the latest

Responses

This year we managed to get answers from 1,140 individuals. Less than last year, but still decent. We did everything we could to make users respond to the survey.

Since respondents are free to skip individual questions, each particular question section below will list how many that actually responded.

A big thanks of course go to all you who donated valuable time to give us this feedback that then allows me to do this analysis and draw conclusions. It truly helps.

As per usual, most respondents say they did not answer the survey last year, which is partly good because it makes sure we get a lot of fresh answers but it is also a failure that we cannot manage to reach out to the same people again.

As can be seen in the trend graph, this year was quite similar to past years:

Continents

1,120 responses

The respondents come primarily from Europe, almost two thirds. It could be noticed that among the top contributors to curl, Europeans are in a majority as well.

The distribution over specific continents has remained oddly stable over past surveys as well.

Protocols

1,130 responses

In this survey, we consider URL schemes to be protocols for simplicity. Which of the twenty-eight supported ones did the respondents use? Or at least say they used, because in the curl team we often doubt some of the numbers in here.

HTTPS and HTTP are the undisputed protocol kings in the curl universe, and the ones following are fairly stable as well. The steep usage difference between number two and number three is really visible in a bar graph like this.

FTP use has gradually been shrinking for many years. The WebSocket protocols that were newcomers in the curl family in 2023 are now the 6th and 7th most used.

No less than seven protocols are below two percent usage and in fact only seven are used more than by ten percent of the respondents.

The median number of protocols people use curl for is two, which certainly means that for most users it only does HTTPS and HTTP. It also means that 45% of users use other protocols as well in addition to those two.

Platforms

1,132 responses

At 96.2% share, almost every survey respondent uses curl on Linux as it remains the top platform curl is used on. The top-5 platforms remain the same, in the same order as they have been for the last several years. I cannot say that I see any reason this is likely to change in coming years either…

Windows bumped back a little from their quite drastic “fall” last year.

As always, it is interesting to see and perhaps questionable, if the ones selecting the most ancient operating systems in this question are actually telling the truth.

Number of platforms

1,128 responses

How many platforms do you use curl on? Less than a quarter of the respondents use it only on a single platform.

Windows versions

560 responses

This year Windows 11 finally overtook Windows 10 as the most common Windows version used when curl runs on Windows. Should we believe that there are still users running curl on Windows 95?

588 responses

Which architecture users are using curl on Windows on was a new question in 2024 so there is not too much history here, but we can still see how the 32 bit x86 usage shared dropped a little to a mere 7% now.

Container

1,089 responses

We have been providing container versions of curl for several years by now. Is it used and which flavor do people prefer?

80.5% of respondents had not used it, but that means that almost out of five (19.5%) has! Many do not have a preference for which to use, but among those that do, docker is a clear winner.

Building curl

1,127 responses

79.9% answered they do not build curl themselves. I have excluded those from the selection out of which I made the graphs below for.

configure remains the top choice of build flavor if we exclude the even larger group of people that build curl using their distro - who then presumably just run with what they use.

There might be a longer trend that makes the configure share slowly go down, so this is something to keep an eye on in the coming years.

I must say that it is curious that %5 don’t know.

Features

908 responses

What do people do with curl? The answers to this question often raises some eyebrows in the style of “huh, that many use X?” and “huh, only Y use feature F!”.

This year we see HTTPS proxy make a fair climb (to 31.5%) as HTTP/2 remains much used (73%) and HTTP/3 stays at 30%.

TLS backends

1,096 responses

At the time of this year’s survey, curl supported 13 different TLS backends in its latest release. But of course, respondents might have used older curl releases that still had support for now removed TLS libraries.

Interesting this year is perhaps that as I write this analysis, we have dropped support for Secure Transport and BearSSL. Secure Transport is the 4th most selected backend this year at 15.5%.

As always, OpenSSL leads this race far ahead of everyone else. This however with a minor caveat: many users of OpenSSL forks may also wrongly select this, thus artificially inflating this a bit.

Because OpenSSL is in a league of its own here, I also produced a graph that compares the other most used libraries when OpenSSL is removed from the graph to make them a little more visible.

SSH backends

930 responses

curl supports three SSH backends and this is the first year we ask about which SSH backend they use. libssh2 is the winner.

QUIC and HTTP/3 backends

925 responses

curl supported four different QUIC backends at the time the question was asked.

The ngtcp2 one is the only non-experimental backend among the bunch. I suspect a certain number of respondents selected OpenSSL-QUIC erroneously, not being able to tell the difference. The msquic backend does not really work so the 1.2% who selected that option must be special people.

curl use

1,107 responses

This is the year curl turned 27 years old. (Even though sometimes we count the birth from the first date in 1996 when the precursor httpget was released.) The general sense is that we have quite satisfied and loyal users. curl mostly delivers on its promises and is a solid and trusted tool. Many of our users have used curl during their entire computer lives.

A few years back we introduced an answer alternative for 18 years or more as previously 12 years or more was the top alternative. It makes sense that the older alternatives get more answers over time and I think it is good news that we still get newcomers.

Every 6th respondent says they used curl for 18 or more years!

curl version

981 responses

When the survey went up, curl 8.13.0 was the latest published release, even if there was an rc build of 8.14.0 out (which many people mentioned to me they actually used but could select in the survey).

Almost two thirds, 63.4% use versions from the last twelve months period. The median release was 8.12, the second newest!

(There is a bug here: the “8.10” version got absorbed into “8.1” because of how Google forms plus Google sheet “helpfully” consider them the same number.)

Favorite command line options

724 responses

This is of course a question mostly for fun and is hard to do anything scientific with. The free text nature of the answer form also adds to the problem of doing analysis on it. I did my test and have tried to accumulate mentions of options to the short version of them if they have one.

At the end of this analysis you can also find many helpful answers to the question: Which curl command line option do you think needs improvement and how?

Used channels

877 responses

Where do users learn and talk about curl? This question tends to be more where do the people who found the curl user survey and responded to it, also find information about curl related things?

This is a question with answers that have changed a lot of the years and they keep changing. Mastodon and Daniel’s blog have climbed up far as the primary curl information channels.

GitHub as well as the mailing lists have fallen in popularity from their hay days.

Channels to use

733 responses

Related is where people would like the curl project to be more visible and which communication channels to use more going forward.

Maybe the biggest discrepancy between these two questions is that 1.5% seem to be using Bluesky now, but 16.5% want us to use it more.

Accessing libcurl

949 responses

libcurl is the network transfer engine of the command line tool and is commonly accessed by users via bindings. The bindings are what makes libcurl truly accessible to almost all developers everywhere. Which ones do people use?

85.7% of the respondents this year say they use curl, the command line tool, so presumably at least some of them only use libcurl (or neither).

The graphs below show libcurl binding usage among the respondents.

Contribution

989 responses

Users contribute to curl to a large degree. Maybe this question tells us more about the particular user population that answered the survey than what it says about curl users in general.

How did the respondents contribute to the project?

Why not contribute more?

1,072 responses

Why do the respondents not contribute (more) to the project we asked.

curl of course is in competition with every other Open Source project for contributors’ time and attention, but also with everything else in life, like YouTube, games and TV shows.

By having an idea what the major obstacles are for more contributions, maybe there is something we can do?

Other Open Source

1,104 responses

The respondents are to a large degree involved in other Open Source projects than curl. Perhaps in addition to.

How good is the curl project

We asked the respondents to grade how good the curl project is to handle things in seven different areas. 1 is the worst, 5 is the best. To compensate for the fact that there are different amounts of answers to each section, we count selection by percent.

Participation:

section number of responses
patches and pull-requests 243
bug reports 275
female contribs and minorities 129
attribution and giving credits 292
helping newcomers 198
information 362
security 412

Here is the overview of how the scoring was done for the 2025 answers

Converting those into a single score per section, then comparing that single score with how people answered these questions in the past

The general pattern seems to remain: we are best at security. This year bug reporting surpassed giving credits, but both are still scored very high.

Our primary weak spot is “handling minorities”, whatever that actually means. We are certainly bad at having a diverse representation among top contributors and project leadership.

The “handling newcomers” is the second worst plot but at least it took a significant bump up this year, and with a score above 4.0 it cannot be that bad, can it?

Remain on GitHub

1,120 responses

This question was added to the survey because it has been brought up in the community once in a while recently so it was interesting to get a sense for what people in general think.

Clearly people don’t have a lot of strong feelings for this. Only one in five said yes and roughly as many said no, and the rest were indifferent or did not know…

Best areas

938 responses

Asked to select up to four areas where curl is best, this is the distribution.

Worst areas

159 responses

Asked to select up to four areas where curl is worst, this is the distribution. The options are the exact same as in the “best areas” question above.

The idea behind this question is to help us figure out which areas perhaps need more attention than others. Where we should improve.

If you couldn’t use libcurl, what would be your preferred transfer library alternatives?

918 responses

This question is meant to give us a picture of which libraries and options that are the biggest “competitors” always keep us puzzled because so many respondents actually say they would use code from wget , which in my book is close to “homegrown” but the latter only gets 6.0% of the responses.

This year we got a few write-ins for hyper/reqwest that made me add that to the graph. It clearly should have been a provided option from the start.

The longer name for “native language lib” is “native lib in Perl, Python, Java, Go, Rust, JavaScript etc”

The wget and native lib options have clearly increased in popularity as libcurl alternatives in recent years.

Which other download utilities do you normally use?

1,039 responses

These other tools are partly competing alternatives to curl, but in many cases they of course instead offer tangental and additional functionality for the toolbox. Three out of four curl users also use wget.

This year xh and rclone were added as write-ins so often I decided to add them to the graph.

Which of these features would you like to see curl support?

861 responses

This is a question we repeat every year, but the answer alternatives tend to vary so much that a regular “development” graph for them makes less sense here.

The answers here help guide us in the years to come what to focus on and what maybe is less important.

Which of these APIs would you use if they existed in libcurl?

505 responses

Maybe this list can serve as an indicator of what libcurl users want from libcurl. Although it is a little vague for some of them exactly what the options mean, and I think some of them are not likely to ever actually get implemented…

As with all questions, it is of course easy to select it in a survey without much extra consideration.

Have you used the trurl tool?

1,049 responses

More of an information than a genuine question perhaps, but we asked last year as well and then 6.6% said yes. This year it moved up a tiny bit.

Have you used the wcurl tool?

1,046 responses

wcurl recently was made to get released as part of the curl tarball so it should now be more accessible and easy to use for many users. This was the premiere for this question and it shows that wcurl is not yet too widely used.

By your estimate, how many installations would you say curl and libcurl run in?

778 responses

I admit that this question was a little tongue-in-cheek, and since it was a free text field it is not really possible to do much with the responses here. If we keep this question in the survey next year, I think we should only allow numbers or maybe offer a wide range of pre-selected alternatives.

We got answers ranging from 1 (yeah, always the jokers) to 100 billion and eternity.

Which question would you like to see in this survey next year?

73 responses

If you miss support for something, tell us what!

58 responses

Which curl command line option do you think needs improvement and how?

147 responses

This is a filtered and curated list of the free text answers we received.

Anything else you think we should know?

277 responses

This open-ended field turns out to be used primarily for people to say thank you and expressions grattitude. Truly ego-boosting to read, but since they do not actually contribute to the analysis I have filtered out most of that from this curation.