blockchain.info's wallet allows (or used to) one to access funds on the above, but it has been a long time since I did that, and I do not know if more modern versions still allow that.
You can still do that in "
Settings Icon->Wallets & Addresses", below the page, there's an "
Import Bitcoin Addresses" button, you can paste a compressed private key instead if you want it to be spendable.
You have the option to "
Transfer funds to an existing wallet" (
sweep) it to your existing wallet or not, if not "
swept" you'll have an option to select that wallet in the 'send' page.
But there's a limitation: you can only import
legacy addresses, not SegWit or P2SH.
The consensus here is to keep away from an online wallets anyways, but it's up to you..