How much small are delta updates?

Typically they are about 10 MB, but it depends on how many changes has been made between the old and the new version. Sometimes it may be low as 5 MB, and sometimes a bit bigger, about 30 MB.
Before start downloading the delta update, you can always see the exact size of the data to be downloaded, so you can decide if download it or not.

What kinds of recovery does CyanDelta support?

CyanDelta supports TWRP recovery and CWM-based open-source recoveries (they are the open-source version of ClockworkMod recovery)

CyanDelta failed to install a zip in recovery on my device!

You probably have the official closed-source ClockworkMod recovery. It’s not supported by CyanDelta because his author has locked it to only work with his proprietary app “ROM Manager”, so we are unable to support it.
If you have that recovery you can replace them with the TWRP recovery (download from here: http://teamw.in/project/twrp2 ) or a CWM-based recovery. Otherwise you can just manually install the zip files generated by CyanDelta.

To use CyanDelta with nightly builds, I must update everyday?

No! It’s not necessary to always update to every new build. You can update only when you want, for example when you see something interesting in the changelog. Currently our server makes deltas between the 40 precedent builds, so for example if you use nightlies, you will always get delta updates unless you have a 40 days old version. If your version becomes too old to get delta updates, you will need to download the new full zip from your ROM website and import it in CyanDelta.

CyanDelta says “Zip not present in our database, ....”, why?

This may be caused by several reasons:
  1. If you have just imported in CyanDelta a zip you just downloaded from your ROM website, it might not have been imported yet in our database, wait some minutes or hours and then re-open CyanDelta.
  2. If you have just imported in CyanDelta a zip that you didn’t downloaded from your ROM website, it’s almost certanly a unofficial CyanogenMod build that is not supported by CyanDelta.
  3. If you have a zip that you didn’t update since a lot of time (40 days for nigthly builds, many months for others), it might not be supported anymore by CyanDelta. This means that you must manually download from your ROM website the new zip and import them in CyanDelta.

I'm using a cm12.1 ROM. Why I don't get updates for cm13?

cm12.1 is a different "branch" from cm13.
For safety reasons, if you want to upgrade you need to:
  1. Download a full cm13 zip from download.cyanogenmod.org website
  2. Manually install the zip via recovery (following CM devs instructions about how to upgrade from cm12.1 to cm13; for example you might need to flash GApps)
  3. Add the new zip to Cyandelta app, then you will start to get delta updates from Cyandelta

Can you give me step-by-step instructions to use CyanDelta?

  1. Install CyanDelta from Google Play.
  2. Download from CyanogenMod website the .zip file of the ROM you are using.
  3. Launch CyanDelta and select the .zip file you just downloaded from CM website. CyanDelta will import them and will create a new bigger zip in “Cyandelta” directory in the root of sdcard.
  4. When an update will be available, a notification will appear. Now you can launch CyanDelta and start the download by simply clicking a button!
  5. The new zip will be placed in “Cyandelta” dir in the root of sdcard. Now you can install it manually from recovery, or you can press “Install zip”. Cyandelta will automatically reboot to recovery, install the zip, wipe cache partition and reboot (this requires root permission).

On what devices and what ROMs does CyanDelta works?

CyanDelta works on all ARM devices running all official versions of CyanogenMod, OmniROM and Paranoid Android. For the moment CyanDelta doesn’t work on x86 devices because it uses a native ARM binary of xdelta3.

Does CyanDelta works with my recovery?

CyanDelta can automatically install new zips in TWRP and CWM-based recoveries. If you have an unsupported recovery, you can simply use CyanDelta to download the new updated zip and then install it manually in recovery, it’s in Cyandelta directory.
The official ClockworkMod recovery it’s not supported because it’s closed-source and it’s locked down by his author to only work with ROM Manager (doesn’t support extendedcommand scripts). The CWM-based recoveries are identical to original ClockworkMod, but they are completely open-source and support extendedcommand scripts, so they work with CyanDelta.

Is CyanDelta secure?

CyanDelta has been designed from the beginning with security and safety in mind. If you are connected through a public untrusted network (a public wifi hotspot) it’s a lot more secure than download zips from a non-HTTPS website.
When the CyanDelta app on your phone connect to our server to get updates, it downloads a JSON with update infos signed with our RSA 2048 bit key, that contains SHA1 hashes of the delta files downloaded by our server. In this way we have a HTTPS equivalent security, although we use HTTP for efficiency reasons.
When the app generate a new updated zip, it will always check if his hash match with the one written in the signed JSON, so data will not get corrupted.

What happens if something fails while installing zips in recovery using CyanDelta?

Theorically the recovery will simply not install the new zip, so it will not damage anything. However since is impossible to test that in all existing devices, there may be strange bugs in your device that might theorically corrupt your data and make your device unable to boot. Unfortunately we can’t prevent this, so you always use this feature at your own risk.
Before installing a zip with CyanDelta for the first time, we suggest you to do a nandroid backup manually.

What happens if the new ROM I have just installed doesn’t boot or it’s unusable?

We know that you want to always use the latest cutting-edge most experimental and unstable ROM! And we know that sometimes these updates can suddently leave you with an unusable device.
To prevent this, CyanDelta always keep one zip file of a previous version of the ROM you are installing. So if the new ROM doesn’t work, simply go to the recovery, reinstall the old zip et voilà!
Thanks to this, we think it’s reasonably safe to update your ROM even without making a nandroid backup every time before flashing.

Why the generated zips by CyanDelta have different size and MD5/SHA1 than the official CyanogenMod zips?

Because zip files generated by CyanDelta are not compressed. Since data is stored uncompressed inside these zip files, they are bigger and obviously they have different hash too.
We have to do that because delta files generated between two uncompressed zips, are a lot smaller than between two compressed ones.

I don’t trust you! If the MD5 is different than the official CyanogenMod zips, who assures me that you haven’t tampered zips?

The content of our zip files and official ones are exactly the same. You can verify that by comparing the hash of every file inside the zip.
Zips produced by CyanDelta are identical (have the same MD5) for all our users, so everybody can verify if the files have been tampered, and in this case alert the whole community.

Can you add support for the ROM **** ?

Maybe, provided that it's used by a sufficiently high number of users, and that they are completely free to redistribute by us. We will not accept anything that is based on non-free ROMs released by device manufacturers.
If you are a ROM developer that comply with these conditions and you are interested to make your ROM supported by CyanDelta, please contact us.