5 ms·

Agreed! multiple times I wasted hours figuring out what selectors to use, but then remembered that I can just look at the network tab and have perfectly structu

Agreed! multiple times I wasted hours figuring out what selectors to use, but then remembered that I can just look at the network tab and have perfectly structured JSON data.

spaniard89277 3y ago
But what if their backend blocks you? I'm trying to develop a instagram scraper and I find that I'll have to spend money on rotating proxies. It doesn't matter if you scrape the DOM or get some Json. I just need to scrape some public account posts and, I may be dumb, but I dunno how to do that with the official APIs (developers.facebook is hard to understand for me).
- Raed667 3y ago
  Instagram is notoriously hard to scrape. I was talking more about random SPAs that you can find. For Instagram, here is a link that maybe helps: https://apify.com/apify/instagram-profile-scraper https://apify.com/apify/instagram-profile-scraper
- blister 3y ago
  Hah, I literally just fought this for the past month. We run a large esports league that relies on player ranked data. They have the data, and as mentioned above, they send it down to the browser in beautiful JSON objects. But they're sitting behind Cloudflare and aggressively blocking attempts to fetch data programmatically, which is a huge problem for us with 6000+ players worth of data to fetch multiple times every 3 months. So... I built a Chrome Extension to grab the data at a speed that is usually under their detection rate. Basically created a distributed scraper and passed it out to as many people in the league as I could. For big jobs when we want to do giant batches, it was a simple matter of doing the pulls and when we start getting 429 errors (rate limit blocking code they use), switch to a new IP on the VPN. The only way they can block us now is if they stop having a website. Give one of the commercial VPN providers a try. They're usually pretty cheap and have tons of IPs all over the place. Adding a "VPN Disconnect / Reconnect" step to the process only added about 10 seconds per request every so often.
  - throwawayadvsec 3y ago
    a VPN won't do anything to help you with instagram the best of the best are 4G rotating proxies the fingerprint needs to change also
  - kbenson 3y ago
    It probably doesn't save you much, since you already built the chrome extension, but having done both I found that tampermonkey is often much easier to deal with in most cases and also much quicker to develop for (you can literally edit the script in the tampermonkey extension settings page and reload the page you want it to apply to for immediate testing).
    - sublinear 3y ago
      I might be wrong, but some sites can block 'self' origin scripts by leaving it out of the Content Security Policy and only allowing scripts they control served by a CDN or specified subdomain to run on their page. Not sure when I last tried this and on what browser(s). You'd have to disable CSP manually in your browser config to make it work, but that leaves you with an insecure browser and a lot of friction for casual users. Not sure if you can tie about:config options to a user profile for this use case. Distributing a working extension/script is getting harder all the time.
      - kbenson 3y ago
        I don't recall if I've encountered that specific problem in tampermonkey (or if I did and it didn't cause a problem worth remembering), but you can run things in the extension's context as well to bypass certain restrictions, as well as use special extension provided functions (GM_* from the greasemoney standard) that allow for additional actions. I do recall intercepting requests when I used a chrome extension to change CSP values though and not needing to when doing something similar later in tampermonkey, but it may not have been quite the same issue as you're describing, so I can't definitively say whether I had a problem with it or not.
- ricardo81 3y ago
  There are plenty sites that do that. And if you're determined to scrape [a website], sometimes it needs proxies, rotating user agents and some rate limiting. Using a full blown browser sometimes helps prevent you hitting those rate limits, but they're still there.
- throwawayadvsec 3y ago
  Instagram data is really valuable and they don't like sharing it, you're not dumb! rotating proxies are the way to go with insta, you can't do much about IP blocking besides using the right IPs although in theory if you had an account(s) you could still scrape data from a datacenter IP(aws), even though the limits were lower than a 4G proxy you can buy/create insta accounts for less than a $ using throwaway phone numbers
- kbenson 3y ago
  You can buy proxies to use, of varying quality, but they are somewhat expensive depending on what you need. I'll just say that firefox still runs tampermonkey, and that includes firefox mobile, so depending on how often you need a different IP and how much data you're getting, you might be able to do away with the whole idea of proxies and just have a few mobile phones that can be configured as workers that take requests through a tampermonkey script. Or that a laptop tethers to that does the same, or that runs puppeteer itself. It depends on whether a worker needs a new IP every few minutes, hours or days as to whether a real mobile phone works (as some manual interaction is often required to actively change the IP).
- paulddraper 3y ago
  > I dunno how to do that with the official APIs Instagram deliberately nuked their own APIs. IDK exactly why, I think it had to do with the 2016 U.S. election.
- deleted 3y ago
  [deleted]
dunham 3y ago
Sometimes that stuff ends up in the cache too, and you can write a script to scrape the cache.
btown 3y ago
For those curious about how this can work in production, Puppeteer's setRequestInterception and page.on('response') are incredibly powerful. Platforms like Browserless can make this easy to orchestrate as well. Also, many full-stack JS frameworks will preload JSON payloads into the initial HTML for hydration. There are tons of possibilities beyond DOM scraping. That said, it's surprising how many high-traffic sites still use "send an HTML snippet over an AJAX endpoint" - or worse yet, ASP.NET forms with stateful servers where you have to dance with __VIEWSTATE across multiple network hops. Part of the art of scraping is knowing when it's worthwhile to go down these rabbit holes, and when it's not!
- ricardo81 3y ago
  The point was, you don't have to wait for JS to re-arrange the dom, sometimes it's a simple request to example.com/api/endpoint?productid=123 and you have all the data you need. No worries about HTML markup.
  - kbenson 3y ago
    I think btown's point was sometimes what you're served is not just "the data you need" from that request, but a portion of the page that will be inserted, rather than built from raw data and inserted, so you need to parse the HTML in the response given since it's an HTML snippet. It's still generally easier, because you don't have to worry about zeroing in on the right section of the page before you start pulling the data out of the HTML, but not quite as easy as getting a JSON structure.
    - ricardo81 3y ago
      I'd disagree on the easier. Instead of loading 100x assets per thing you want to scrape, 2x is way better for both parties. But perhaps if there's xx endpoints for some inefficient reason, the browser DOM would be better.
      - kbenson 3y ago
        I think you're still misunderstanding. Sometimes, sites haven't adopted a pure data-driven model, and when example.com/api/endpoint?productid=123 is requested it doesn't return JSON for the product with id 123, but instead returns a div or table row of HTML which has the data for that product already in it, which is then inserted directly where it's meant to be in the current page, rather then built into HTML from JSON and then inserted. What I was saying is that method is not quite as easy as pure JSON to get data from, but still easier to parse and find the specific data for the specific item you're looking for, as it's a very small amount of markup all related to the entry in question. My interpretation of btown's comment is along the same lines, that it's surprising how many sites still serve HTML snippets for dynamic pages.
commandlinefan 3y ago
> look at the network tab The challenge there is automating it, though - usually the rest endpoints require some complex combination of temporary auth token headers that are (intentionally) difficult to generate outside the context of the app itself and expire pretty quickly.
- Raed667 3y ago
  You can use the application context, while also automatically intercepting requests. Best of both worlds. puppeteer: https://pptr.dev/api/puppeteer.page.setrequestinterception https://pptr.dev/api/puppeteer.page.setrequestinterception playwright: https://playwright.dev/docs/network#network-events https://playwright.dev/docs/network#network-events
  - halJordan 3y ago
    And the article is about using puppeteer ...
- ricardo81 3y ago
  In browsers 'copy as curl' is decent enough. Do the request through a command line. If there's ephemeral cookies, they tend to follow a predictable pattern.
- paulddraper 3y ago
  That's true....but that was already true. Whatever method you were using before SPAs to authenticate your scraper (HTTP requests, browser automation), you can use that same method now.
- z3t4 3y ago
  Static files are much easier to scrape. Its even easier to scrape a static page then it is to use api's
- 1vuio0pswjnm7 3y ago
  Care to provide some examples. The majority of sites submitted to HN do not even require cookies let alone tokens in special headers. A site like Twitter is an exception not the general rule.
1024core 3y ago
These days people are hiding network activity too. For example, I couldn't find how to download the data powering the salary table here: https://sfstandard.com/2023/08/02/see-what-san-franciscos-top-officials-got-paid-last-year-2023-fiscal-year/ https://sfstandard.com/2023/08/02/see-what-san-franciscos-to...
- buzer 3y ago
  It's in iframe. In Firefox right click table, This Frame - Show only this frame. That opens https://datawrapper.dwcdn.net/32i0b/1/ https://datawrapper.dwcdn.net/32i0b/1/. In there you can see it makes request to https://datawrapper.dwcdn.net/32i0b/1/dataset.csv https://datawrapper.dwcdn.net/32i0b/1/dataset.csv
  - 1024core 3y ago
    Thank you! :-)
- slaymaker1907 3y ago
  It's the item called "dataset.csv" in the network tab using Edge devtools.
- duderific 3y ago
  Huh? In network tab in Chrome devtools, there are fetches for dataset.csv - the url is https://datawrapper.dwcdn.net/32i0b/1/dataset.csv https://datawrapper.dwcdn.net/32i0b/1/dataset.csv which downloads the dataset.

Agreed! multiple times I wasted hours figuring out what selectors to use, but then remembered that I can just look at the network tab and have perfectly structured JSON data.

spaniard89277 3y ago

But what if their backend blocks you? I'm trying to develop a instagram scraper and I find that I'll have to spend money on rotating proxies. It doesn't matter if you scrape the DOM or get some Json. I just need to scrape some public account posts and, I may be dumb, but I dunno how to do that with the official APIs (developers.facebook is hard to understand for me).

Raed667 3y ago
Instagram is notoriously hard to scrape. I was talking more about random SPAs that you can find. For Instagram, here is a link that maybe helps: https://apify.com/apify/instagram-profile-scraper https://apify.com/apify/instagram-profile-scraper
blister 3y ago
Hah, I literally just fought this for the past month. We run a large esports league that relies on player ranked data. They have the data, and as mentioned above, they send it down to the browser in beautiful JSON objects. But they're sitting behind Cloudflare and aggressively blocking attempts to fetch data programmatically, which is a huge problem for us with 6000+ players worth of data to fetch multiple times every 3 months. So... I built a Chrome Extension to grab the data at a speed that is usually under their detection rate. Basically created a distributed scraper and passed it out to as many people in the league as I could. For big jobs when we want to do giant batches, it was a simple matter of doing the pulls and when we start getting 429 errors (rate limit blocking code they use), switch to a new IP on the VPN. The only way they can block us now is if they stop having a website. Give one of the commercial VPN providers a try. They're usually pretty cheap and have tons of IPs all over the place. Adding a "VPN Disconnect / Reconnect" step to the process only added about 10 seconds per request every so often.
- throwawayadvsec 3y ago
  a VPN won't do anything to help you with instagram the best of the best are 4G rotating proxies the fingerprint needs to change also
- kbenson 3y ago
  It probably doesn't save you much, since you already built the chrome extension, but having done both I found that tampermonkey is often much easier to deal with in most cases and also much quicker to develop for (you can literally edit the script in the tampermonkey extension settings page and reload the page you want it to apply to for immediate testing).
  - sublinear 3y ago
    I might be wrong, but some sites can block 'self' origin scripts by leaving it out of the Content Security Policy and only allowing scripts they control served by a CDN or specified subdomain to run on their page. Not sure when I last tried this and on what browser(s). You'd have to disable CSP manually in your browser config to make it work, but that leaves you with an insecure browser and a lot of friction for casual users. Not sure if you can tie about:config options to a user profile for this use case. Distributing a working extension/script is getting harder all the time.
    - kbenson 3y ago
      I don't recall if I've encountered that specific problem in tampermonkey (or if I did and it didn't cause a problem worth remembering), but you can run things in the extension's context as well to bypass certain restrictions, as well as use special extension provided functions (GM_* from the greasemoney standard) that allow for additional actions. I do recall intercepting requests when I used a chrome extension to change CSP values though and not needing to when doing something similar later in tampermonkey, but it may not have been quite the same issue as you're describing, so I can't definitively say whether I had a problem with it or not.
ricardo81 3y ago
There are plenty sites that do that. And if you're determined to scrape [a website], sometimes it needs proxies, rotating user agents and some rate limiting. Using a full blown browser sometimes helps prevent you hitting those rate limits, but they're still there.
throwawayadvsec 3y ago
Instagram data is really valuable and they don't like sharing it, you're not dumb! rotating proxies are the way to go with insta, you can't do much about IP blocking besides using the right IPs although in theory if you had an account(s) you could still scrape data from a datacenter IP(aws), even though the limits were lower than a 4G proxy you can buy/create insta accounts for less than a $ using throwaway phone numbers
kbenson 3y ago
You can buy proxies to use, of varying quality, but they are somewhat expensive depending on what you need. I'll just say that firefox still runs tampermonkey, and that includes firefox mobile, so depending on how often you need a different IP and how much data you're getting, you might be able to do away with the whole idea of proxies and just have a few mobile phones that can be configured as workers that take requests through a tampermonkey script. Or that a laptop tethers to that does the same, or that runs puppeteer itself. It depends on whether a worker needs a new IP every few minutes, hours or days as to whether a real mobile phone works (as some manual interaction is often required to actively change the IP).
paulddraper 3y ago
> I dunno how to do that with the official APIs Instagram deliberately nuked their own APIs. IDK exactly why, I think it had to do with the 2016 U.S. election.
deleted 3y ago
[deleted]

dunham 3y ago

Sometimes that stuff ends up in the cache too, and you can write a script to scrape the cache.

btown 3y ago

For those curious about how this can work in production, Puppeteer's setRequestInterception and page.on('response') are incredibly powerful. Platforms like Browserless can make this easy to orchestrate as well. Also, many full-stack JS frameworks will preload JSON payloads into the initial HTML for hydration. There are tons of possibilities beyond DOM scraping. That said, it's surprising how many high-traffic sites still use "send an HTML snippet over an AJAX endpoint" - or worse yet, ASP.NET forms with stateful servers where you have to dance with __VIEWSTATE across multiple network hops. Part of the art of scraping is knowing when it's worthwhile to go down these rabbit holes, and when it's not!

ricardo81 3y ago
The point was, you don't have to wait for JS to re-arrange the dom, sometimes it's a simple request to example.com/api/endpoint?productid=123 and you have all the data you need. No worries about HTML markup.
- kbenson 3y ago
  I think btown's point was sometimes what you're served is not just "the data you need" from that request, but a portion of the page that will be inserted, rather than built from raw data and inserted, so you need to parse the HTML in the response given since it's an HTML snippet. It's still generally easier, because you don't have to worry about zeroing in on the right section of the page before you start pulling the data out of the HTML, but not quite as easy as getting a JSON structure.
  - ricardo81 3y ago
    I'd disagree on the easier. Instead of loading 100x assets per thing you want to scrape, 2x is way better for both parties. But perhaps if there's xx endpoints for some inefficient reason, the browser DOM would be better.
    - kbenson 3y ago
      I think you're still misunderstanding. Sometimes, sites haven't adopted a pure data-driven model, and when example.com/api/endpoint?productid=123 is requested it doesn't return JSON for the product with id 123, but instead returns a div or table row of HTML which has the data for that product already in it, which is then inserted directly where it's meant to be in the current page, rather then built into HTML from JSON and then inserted. What I was saying is that method is not quite as easy as pure JSON to get data from, but still easier to parse and find the specific data for the specific item you're looking for, as it's a very small amount of markup all related to the entry in question. My interpretation of btown's comment is along the same lines, that it's surprising how many sites still serve HTML snippets for dynamic pages.

commandlinefan 3y ago

> look at the network tab The challenge there is automating it, though - usually the rest endpoints require some complex combination of temporary auth token headers that are (intentionally) difficult to generate outside the context of the app itself and expire pretty quickly.

Raed667 3y ago
You can use the application context, while also automatically intercepting requests. Best of both worlds. puppeteer: https://pptr.dev/api/puppeteer.page.setrequestinterception https://pptr.dev/api/puppeteer.page.setrequestinterception playwright: https://playwright.dev/docs/network#network-events https://playwright.dev/docs/network#network-events
- halJordan 3y ago
  And the article is about using puppeteer ...
ricardo81 3y ago
In browsers 'copy as curl' is decent enough. Do the request through a command line. If there's ephemeral cookies, they tend to follow a predictable pattern.
paulddraper 3y ago
That's true....but that was already true. Whatever method you were using before SPAs to authenticate your scraper (HTTP requests, browser automation), you can use that same method now.
z3t4 3y ago
Static files are much easier to scrape. Its even easier to scrape a static page then it is to use api's
1vuio0pswjnm7 3y ago
Care to provide some examples. The majority of sites submitted to HN do not even require cookies let alone tokens in special headers. A site like Twitter is an exception not the general rule.

1024core 3y ago

These days people are hiding network activity too. For example, I couldn't find how to download the data powering the salary table here: https://sfstandard.com/2023/08/02/see-what-san-franciscos-top-officials-got-paid-last-year-2023-fiscal-year/ https://sfstandard.com/2023/08/02/see-what-san-franciscos-to...

buzer 3y ago
It's in iframe. In Firefox right click table, This Frame - Show only this frame. That opens https://datawrapper.dwcdn.net/32i0b/1/ https://datawrapper.dwcdn.net/32i0b/1/. In there you can see it makes request to https://datawrapper.dwcdn.net/32i0b/1/dataset.csv https://datawrapper.dwcdn.net/32i0b/1/dataset.csv
- 1024core 3y ago
  Thank you! :-)
slaymaker1907 3y ago
It's the item called "dataset.csv" in the network tab using Edge devtools.
duderific 3y ago
Huh? In network tab in Chrome devtools, there are fetches for dataset.csv - the url is https://datawrapper.dwcdn.net/32i0b/1/dataset.csv https://datawrapper.dwcdn.net/32i0b/1/dataset.csv which downloads the dataset.