Finding a loose dog puts you in charge of an animal who is likely frightened, possibly injured, and one sudden grab away from bolting into traffic or snapping at a kind hand. Reuniting her safely is a sequence: secure her, read what identification she carries, then connect with the people already searching for her — in that order, at her pace.
Secure her without scaring her off
Stop and let her notice you rather than chasing her down; a pursued dog runs, often toward roads. Crouch sideways, avoid looming over her or staring straight at her, and let her come to investigate, using calm talk and, if you have it, food tossed near you rather than held in an outstretched hand she must approach head-on. Slip a lead — or a belt, scarf or spare lead made into a loop — gently over her head once she is close, rather than grabbing for her collar, which is the move most likely to make a nervous dog bite or bolt. If she will not come to you at all, do not force it: note where she is, photograph her if you can, and call the local dog warden or animal control, whose staff have the equipment and experience to catch her safely.
Read the identification she is carrying
Once she is secured, check her collar. A tag with a phone number is the fastest reunion there is: call it while she is safely held, describe where you are, and keep her secured until the owner arrives — an excited dog can slip a loose grip at the sight of them. Ask the caller to describe something about the dog — her collar, a distinctive mark, her name and how she answers to it — before handing her over, because a genuine owner can always do this easily. If there is no tag, or no answer, take her to any veterinarian, who will scan her microchip without charge and contact the registered keeper. Keep her separate from your own dogs meanwhile, offer water and a small meal if she seems hungry, and do not bathe, feed up or treat her beyond comfort — her owner and vet should see her as she was found.
Connect with the search that is already running
Somewhere, usually nearby, her owner is walking streets, phoning vets and posting online. Meet that search halfway: report her to the local dog warden or animal control as soon as you can — in many places this is a legal duty for a finder, and it is also the first place many owners call — and let local shelters and vet practices know you have her. A post in local community groups with her photo, the street where you found her and how to reach you spreads quickly, but withhold one identifying detail from the post so a claimant can prove she is theirs by describing it. If nobody comes forward the same day, the warden or a rescue can take her while the search continues; do not simply keep a found dog or rehome her yourself.
Let her tag do the talking when it can
More dogs now wear scannable identification alongside a printed tag, and it is worth checking her collar for a QR code as well as printed text. A scan opens her profile — who she is, who she belongs to, how to reach them — without you needing her to stand still for a phone number to be read off a wriggling collar, and without the owner relying on a chip scanner being nearby. KinsLe's Verified QR ID Pet Profiles work exactly this way: every pet has a unique QR ID for their collar, and a finder who scans it reaches the profile and the owner.