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I am preparing to give live video courses for newbies about how btc blockchain works. I am willing to use btc testnet network and was looking for a friendly-use btc testnet wallet.
I don't want to use testnet network in one of the popular wallet just to avoid confusions.
I came accross this wallet app but it seems to be complicated more than a real btc wallet: https://play.google.com/store/apps/details?id=de.schildbach.wallet_test&hl=en&gl=US
It gives just one recieving address without having access to seed/private keys/...etc

Do you know any btc testnet wallet for mobile/desktop (not web-wallet) ?
It would be nice if you can give more helpful advices.

Thank you all

Use the below guild for electeum testnet mode,
https://bitzuma.com/posts/a-beginners-guide-to-the-electrum-bitcoin-wallet/#testnet-mode

Testnet Mode
Although Electrum supports Testnet mode, this feature isn’t available through the graphical user interface. Running Electrum in Testnet mode is not difficult, but the procedure varies by operating system.

Specifically, you’ll create an operating system-specific launcher. This launcher can be placed on your desktop or elsewhere. It will allow you to run Testnet Electrum whenever you double click it.

Before setting up an Testnet Electrum launcher, it’s essential to run Electrum at least once in Mainnet mode. That’s best accomplished by double clicking Electrum’s built-in launcher, or using your system launcher. This step adds essential files that Testnet Electrum will need to run.

Testnet on Windows
Copy the Electrum launcher on the desktop (right click, Copy). Paste a new copy onto the desktop (right click, paste). Rename the copy to “Electrum Testnet.”

Access the launcher’s properties (right click, Properties). Under the “Target” field append the following text: “ --testnet” (a leading space is required, and there are two dashes). Click OK.

https://i.imgur.com/gubQvlm.png

To know about testnet mode for Mac OS, you can click the link below for more information.
https://bitzuma.com/posts/a-beginners-guide-to-the-electrum-bitcoin-wallet/#testnet-mode

For more information, there is an article already here on this forum about bitcoin testnet by tranthidung

Bitcoin Testnet. Activate, experience it, but don't trade and get scammed.
https://bitcointalk.org/index.php?topic=5215716.0

Why not use a popular wallet instead so that if they are going to use a real wallet just tell them to switch them into mainnet it won't be a problem.

Electrum testnet should be the best option for the desktop you can check this video below how to setup testnet on Electrum.
- https://www.youtube.com/watch?v=iQLx6GMwJZo

For mobile check this mycelium testnet below.
- https://play.google.com/store/apps/details?id=com.mycelium.testnetwallet&hl=en&gl=

Coinomi is another option you can just search it on Google play store.

For desktop, I suggest Electrum or BitPay.
To activate the testnet mode on BitPay, follow this guide:
https://support.bitpay.com/hc/en-us/articles/360015463612-How-to-Create-a-Testnet-Wallet

For Android, you can either use Coinomi or Mycelium testnet wallet.
To create a testnet wallet on Coinomi, tap the (+) button then choose "add coins", from the coins list choose "Bitcoin Test BTCt"

if you decided to use any wallet like Coinomi that is closed source, please remember to discourage your viewers from using such wallets due to their inherent risks.

I wouldn't recommend BitPay wallet since :
1. the community it's relative small, which is troubling when you need help or confused
2. BitPay have many controversial, so it's possible they might do same things to their wallet

If you want to download the latest Bitcoin core (https://bitcoin.org/en/download), already had Bitcoin Testnet wallet on second choice application

https://i.postimg.cc/Prs35mSD/testnet.jpg

you need at least 20GB blockchain (https://en.bitcoin.it/wiki/Testnet)data download before running it. More patiently but you run your own node, it's good to lesson your audience.


for more information: https://bitcointalk.org/index.php?topic=5215716.0

Yep, Bitpay is not a great option.
Bitcoin core needs a large download many newbies are not comfortable with.
I'd say that Electrum is pretty much the best choice, especially on PC, but if you introduce Electrum to newbies please make sure you also tell them about updating safely by downloading from the proper location and verifying the signature.

3. Correct. Just like the payment processor... the wallet won't work if you're in one of these countries:  https://support.bitpay.com/hc/en-us/articles/360000123366-Why-can-t-I-use-BitPay-s-services-in-my-country

A dialog would show when you try to create the wallet, but it will remain frozen until you change your IP address.

@pooya87 and @ETFbitcoin, I totally agree with you. I wouldn't recommend those wallets for mainnet usage for the same reasons you stated above. However, I don't see any inconvenience in using them for learning purposes on the testnet mode and no coins with real value at stake.
Anyway, the choices are limited when it comes to lightweight wallets that support testnet.

The testnet blockchain size, at the moment of writing, is ~25Gb.

Thank you Charles, this is what i am looking for, as there are no wallets dedicated only for testnet. And also because i am an Electrum user since a long time.
Maybe i will also use Mycelium but i can't find any tutorial about how to use it.

After checking the topic made by Tranthidung, i noticed that the client i mentioned in op, which is a mobile based wallet, generates one single address starts with "t", while testnet addresses [legacy] either starts with "m" or "n", right?
The client i tried maybe fake, i will check about it .

Does the address your wallet generated start with tb1? If yes then this is a bech32 testnet address.
Probably your wallet creates native segwit addresses by default!
A legacy testnet address (P2PKH) starts with m or n indeed.

The updated Testnet blockchain size that is on my PC has now reached over 30 GB.
For beginners, I prefer to use Electrum in Testnet mode.

https://talkimg.com/images/2023/05/17/blobfe0319a7d1046e5f.png

Thanks for the correction, I just calculated year from January 2018 where 14 GB blockchain data downloaded, means each year 1,5Gb data x 3 + 14 GB (get false calculated).

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1. Go to Playstore and download Mycelium Testnet Wallet

2. Open and create wallet

https://i.postimg.cc/h4Qc6pvQ/my1.jpg

3. then you will direct to home screen

https://i.postimg.cc/sgjFjcjc/my2.jpg

- Important, you have to back up now your mnemonic seed.
- tap barcode (tap for bech32) for change destination address (Legacy, segwit or native segwit).
- click send and receive button for transaction.

https://i.postimg.cc/ZYwpsY95/my3.jpg https://i.postimg.cc/tJ4PRwcb/my4.jpg

- or use scan button to scanning barcode transaction.

cmiiw

that's true but when you are teaching newcomers and if they end up trying things up using the same wallet that was used in the tutorial they were reading/watching they may continue using it for mainnet too thinking it worked fine there and it was used by the person who was teaching them so it must be OK.

out of curiosity, does that folder contain only the blockchain or does it have other stuff too? since explorers say blockchain size is 23.60 GB.
chainstate, block index, block undo data (i forgot what the file is called in core), wallet files that could also be big if they were used a lot. and all of that can take up a lot of additional size.

Here are the contents of the testnet3 folder on my computer. I didn't add any files manually to the folder.

https://talkimg.com/images/2023/05/17/blob021577f479b46f89.png

I was curious to browse also through explorers (https://tbtc.bitaps.com/), and got data like the following:

https://talkimg.com/images/2023/05/17/blobbe2f6f1936fa61f2.png

It seems that the cause of the data in my testnet3 folder has a larger file size.

^
Do you use testnet that often? I find it hard to understand a difference of over 8 gigs due to transaction history unless you have thousands of transactions. What about block duplicates or something similar?

I have used a bitcoin-core testnet several times for testing transactions but not thousands of transactions. On another occasion, I also used the Windows OS version and the macOS version of Bitcoin Core Testnet using the same testnet3 folder.
Just now, I tried to look again at the contents of the data in the testnet3 folder. I'm not sure if there is duplicated data.

Maybe I will try to re-download the blockchain testnet data from scratch to determine whether the resulting filesize will be the same as what I showed earlier or the same as the data in explorers.

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@OP sorry the discussion widened a little to the blockchain testnet filesize.

Today I tried to re-download the Blockchain testnet from scratch by deleting the old testnet3 folder first.
Currently, I haven't used it for any transactions. Here are the results (last synchronization up to the number of blocks 1862241):

https://talkimg.com/images/2023/05/17/blob0acfcca4775a7c13.png  https://talkimg.com/images/2023/05/17/blobde3bea3344031874.png

thanks for the update.
the blockchain size is the size of the "blocks" file not the entire testnet3 folder because as i said it contains other files that have high sizes:
* chainstate: is the current UTXO list that takes up quite a lot of space because it is ALL the unspent transaction outputs. this file is not part of the "blockchain" and can even be safely deleted, of course you'll have to recreate it from block #1 if you delete it.
* indexes: is not that big but it contains the information about blocks, where they are on your disk, etc. to make look up process faster. again this is not part of the "blockchain" and same as chainstate can be deleted.
* rev files that are found inside blocks folder are the "undo" data that i mentioned before and are used to "undo" the chainstate if needed like in case of chain reorgs. this also takes some some space and is the same as the other two and is not part of the "blockchain".

your blocks folder is showing 28.73 which means out of 33.36 GB there were 4.63 GB chainstate and indexes. your debug.log seems to be moderately big (~0.5GB) which i'm not sure what it does.
the 28.73 GB is closer to 23.6 GB reported by the block explorer. if you could, check the rev files and see how much space they take and only sum the blk***.dat file sizes to see if it is closer to 23.6 or not.

Here's some stats from my testnet node:




As for OP's question:

• electrum can be run on testnet
• wasabi can be run on testnet
• bitcoin core can be run on testnet
• a local copy of coinb.in can be run on testnet
• armory can be run on testnet
• btcd can be run on testnet
• knots can be run on testnet
• a local copy of bitaddress.org can be run on testnet

Take your pick :)
I guess the wallet you pick depends on the tutorial you want to give... Electrum is SPV and has a lot of coin controll options, wasabi has that built in privacy (including a coinjoin gui), core has even more features than electrum and it's a full node, coinb.in has an easy gui to learn the basics of tx creation, armory is built on top of bitcoind, btcd and knots have a little bit different feature set, bitaddress.org teaches about the many representation ways of keys,...

Thanks for the illustration. I think this your advice will go along way to help us to keep our money safe in our wallet.

Thank you for your guidance. The following are the file size for each file type:

https://talkimg.com/images/2023/05/17/blobac3972ebf89075fd.png  https://talkimg.com/images/2023/05/17/blob383500bfa069ef84.png  https://talkimg.com/images/2023/05/17/blobbb8881d428e8f58b.png
1. blk*.dat file sizes
2. rev*.dat file sizes
3. /blocks/index sizes

It seems that the total blk * .dat file size is still larger than 23.6 GB (~ 1.7 GB).