How to manually approve a token for swap on Uniswap (direct contract interaction)

Question

I want to approve token spending on Uniswap for a token I don't own. Uniswap UI won't let me do that (instead it displays a gray out button "insufficient balance").

Seems the only option would be to manually approve the token using Etherscan.

Which Uniswap contract should I interact with? (v2) What are the required parameters and what is the uint for infinite approval?

You want to approve before getting the token? why not just do it once you have it? — Markus - soliditydeveloper.com, Oct 05 '20 at 06:54
Because i need to dump it as fast as possible once i have it. — Pm Rivière, Oct 05 '20 at 07:13

score 10 · Accepted Answer · answered Oct 05 '20 at 07:29

10

Get the pool address

Go to the Uniswap UI at https://app.uniswap.org/. Choose the token pair you want and then click the View pair analytics ↗. This will take you to a link like https://uniswap.info/pair/<poolAddress>. Note down poolAddress.

Approve via Etherscan

Go to https://etherscan.io/token/<tokenAddress>#writeContract where tokenAddress is the one you want to approve. Go to the approve tab and now enter poolAddress + amount.

answered Oct 05 '20 at 07:29

Markus - soliditydeveloper.com

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Thx @markus just a few questions: (1) I want to approve the token for swapping, but still need the pool address right? (2) What value should i give to amount should i fill for infinite approval? – Pm Rivière Oct 05 '20 at 07:31
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@PmRivière (1) Yeah, what did you think? (2) Go for infinite sure. I think even the Uniswap UI does this. – Markus - soliditydeveloper.com Oct 05 '20 at 07:53
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Infinite would mean 2^256 - 1. – Markus - soliditydeveloper.com Oct 05 '20 at 07:54
Just how do i key in 256^-1? it's a UINT256 expected. That would mean i just key in -1? – Pm Rivière Oct 05 '20 at 08:53
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@PmRivière "115792089237316195423570985008687907853269984665640564039457584007913129639935" – Markus - soliditydeveloper.com Oct 05 '20 at 21:13
Uniswap V2 Address is 0x7a250d5630B4cF539739dF2C5dAcb4c659F2488D – jaggedsoft Jan 12 '21 at 15:03
Does anyone knows how to do it on honeyswap? I cannot find view pair analysis button – Marek Feb 17 '21 at 20:09

How to manually approve a token for swap on Uniswap (direct contract interaction)

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